InTechOpen uses cookies to offer you the best online experience. By continuing to use our site, you agree to our Privacy Policy.

Medicine » Oncology » "Osteosarcoma - Biology, Behavior and Mechanisms", book edited by Kanya Honoki and Kurt Richard Weiss, ISBN 978-953-51-3096-3, Print ISBN 978-953-51-3095-6, Published: April 26, 2017 under CC BY 3.0 license. © The Author(s).

Chapter 13

A Dog in the Cancer Fight: Comparative Oncology in Osteosarcoma

By Alexander L. Lazarides, Allison B. Putterman, William C. Eward and Cindy Eward
DOI: 10.5772/66847

Article top


Examples of canine osteosarcoma. (A) and (B) Typical radiographic findings including ill-defined lesions with aggressive periosteal reaction and tumor matrix ossification. (C) and (D) High-grade, highly pleomorphic cells with surrounding osteoid.
Figure 1. Examples of canine osteosarcoma. (A) and (B) Typical radiographic findings including ill-defined lesions with aggressive periosteal reaction and tumor matrix ossification. (C) and (D) High-grade, highly pleomorphic cells with surrounding osteoid.
(A) Gross histology demonstrating a destructive osseous lesion with an associated soft tissue mass, (B) high-grade cellular lesion with a trabecular pattern and osteoid production, (C) radiographic findings demonstrating increased sclerosis, with a large periosteal reaction, and (D) MRI images demonstrating cortical destruction and a large soft tissue mass (images collected with permission) [60].
Figure 2. (A) Gross histology demonstrating a destructive osseous lesion with an associated soft tissue mass, (B) high-grade cellular lesion with a trabecular pattern and osteoid production, (C) radiographic findings demonstrating increased sclerosis, with a large periosteal reaction, and (D) MRI images demonstrating cortical destruction and a large soft tissue mass (images collected with permission) [60].

A Dog in the Cancer Fight: Comparative Oncology in Osteosarcoma

Alexander L. Lazarides1, Allison B. Putterman2, William C. Eward1, 3 and Cindy Eward DVM4
Show details


Since the great Rudolf Virchow advised, “Between animal and human medicine there is no dividing line, nor should there be,” limited attention has been paid to cancer in animals. This is finally changing thanks to a renewed focus on studying pet dogs with cancer. Unlike the laboratory mice who have been the mainstay of animal models of disease, pet dogs share an environment with their human owners, have an intact immune system, and often develop diseases spontaneously in ways that mimic their human counterparts. Osteosarcoma (OSA) – while uncommon in humans - is a common malignancy in dogs. This comparatively high incidence alone renders pet dogs an ideal “model” to conduct translational and clinical research into OSA. Indeed, there are many similarities between the two species with respect to this disease. However, owing to the shorter life span and accelerated disease progression, treatment effects can be assessed much more rapidly in canines than in humans. Overall, dogs represent a unique model to study OSA; this chapter aims to discuss the ways that comparative oncology between dogs and humans are being used from basic science research, to genetics and mechanisms of disease, to tumor biology and finally to developing novel treatments.

Keywords: canine, osteosarcoma, human, comparative oncology, novel treatments, genomic analysis

1. Introduction

Making meaningful advances in osteosarcoma (OSA) therapy has been hindered by the low incidence of the disease in humans. In contrast to the low incidence in humans, OSA is a common malignancy affecting pet dogs. While there are fewer than 1000 new human OSA diagnoses in the USA each year, there no fewer than 10,000 canine cases of OSA every year, by conservative assessments made several decades ago [1, 2]. This relatively high incidence in dogs provides an ideal “model” for conducting translational research and clinical research and for gaining insight into the biology of OSA. This paradigm depends upon canine OSA having specific parallels with human OSA. Indeed, there are many similarities between the two species with respect to this disease: from location of the primary tumors and patterns of metastasis, to the genetic drivers of disease and response to therapy [1]. Because canine OSA is a naturally occurring condition in pets who live alongside us, it arises among the same environmental, dietary and immunologic factors as human OSA. In addition to the similarities, there are several key differences that allow canine OSA to elucidate new information in shorter periods of time. Canine OSA typically displays a more aggressive biology and a much faster rate of metastasis than in humans, with death often occurring within 6 months and with 96% of canine OSA patients dying from the disease [3]. Because of these differences, treatment effects from novel interventions can be seen much more rapidly, with a fraction of the longevity and cost required of human clinical trials. Such comparative, cross-species trials conducted in dogs are often met with enthusiasm by owners and with fewer regulatory hindrances that would face human patients [4]. This field of cross-species cancer research is known as “comparative oncology.” Dogs present to us a unique, powerful and underutilized model to study OSA; this chapter aims to demonstrate and discuss the ways that comparative oncology between dogs and humans with OSA can be used to inform genetics and mechanisms of disease, tumor biology and behavior and the development of novel treatments.

2. Canine osteosarcoma: overview

Osteosarcoma is the most common primary bone tumor in dogs [59]. It is estimated to occur in more than 10,000 dogs each year in the USA [1, 10]. This estimate is likely conservative, as the number of pet dogs has increased dramatically since these early studies of the incidence of canine OSA and there are still many dogs who do not receive medical attention. Canine OSA tends to occur in middle-aged to older dogs (median age of 7 years), with a small number of cases presenting between 18 and 24 months of age [11]. Primary rib OSA occurs in younger adult dogs with a mean age of 4.5–5.4 years [12, 13]. Historically, the incidence of OSA in dogs has been considered to be higher in males than females [3, 57, 11, 14]; however, more recent data suggest an equal sex distribution [15]. Large and giant breed dogs are predominantly affected. The breeds that are most at risk for OSA are Saint Bernard, Great Dane, Irish setter, Doberman pinscher, Rottweiler, German shepherd and golden retriever. Increased weight and, in particular, height appear to be the most predisposing factors [58, 11, 1619]. Many domestic breeds have narrow genetic diversity due to selective breeding practices, which provides a unique opportunity to more clearly elucidate the hereditary basis of OSA in dogs [15, 20].

Approximately 75% of canine OSA occurs in the appendicular skeleton [6, 13]. Commonly affected sites, in order of frequency, include the distal radius, proximal humerus, distal ulna, distal femur, proximal tibia, distal tibia and diaphyseal ulna [21]. Primary OSA in the axial skeleton has also been well characterized, in order of frequency, in the mandible, maxilla, spine, cranium, ribs, nasal cavity and paranasal sinuses and pelvis [13]. As in humans, OSA of extraskeletal sites is rare but has been reported in the mammary tissue, subcutaneous tissue, spleen, bowel, liver, kidney, testicle, vagina, eye, gastric ligament, synovium, meninges and adrenal gland [2228].

Dogs with appendicular OSA often present with lameness and swelling at the affected site. There may be a history of mild trauma prior to the onset of lameness and this may cause an acute exacerbation of clinical signs [15, 21]. The signs associated with axial skeletal OSA are site dependent and vary from localized swelling, dysphagia (oral sites), exophthalmos and pain on opening the mouth (caudal mandibular and ocular sites), facial deformity and nasal discharge (sinus and nasal cavity sites) and hyperesthesia with or without neurologic signs (spinal sites) [15]. Dogs with rib OSA often present because of a palpable mass [15].

3. Genetic factors

Development of canine OSA is characterized by the involvement of sporadic and heritable genetic factors. The most thoroughly described gene mutations in dogs are the p53 and phosphatase and tensin homolog (PTEN) tumor suppressor genes and abnormalities in the Rb family members, Rb, p107 and p130. Approximately 60% of canine OSA cell lines overexpress mutant p53 mRNA and protein, which correlates with the presence of missense point mutations within the DNA-binding domain [29]. These findings are corroborated by the identification of mutations in p53 in 41% of spontaneously arisen OSA tumors. The majority of mutations in these cases were point mutations (74%), with a lesser percentage of mutations being deletions (26%). In the absence of a functional p53 protein, its transcriptional target, mdm2, is not present to destabilize the mutant p53 protein and mutant p53 protein accumulates within the cell [30]. Studies have suggested that the RB gene signaling pathway is dysregulated in canine OSA. Analysis of OSA samples identified copy number loss in 29% of cases, resulting in correlative reduction or the absence of RB protein expression in 62% of samples tested [31]. These findings suggest that aberrations in the RB gene likely participate in formation and/or progression of OSA. In addition to p53 and RB gene abnormalities, genomic loss of the phosphatase and tensin homolog (PTEN) tumor suppressor gene is suspected to participate in the genetic pathogenesis of canine OSA. In vitro studies with canine OSA cell lines found that 60% of the cell lines had mutations in PTEN, resulting in the absence of gene transcription and protein translation [29].

4. Diagnostic work-up: local disease

The diagnostic evaluation for dogs with OSA is similar to that employed in humans. Initial evaluation of the primary site involves radiographs. Lesions are typically characterized by a mixed pattern of cortical lysis and periosteal proliferation; however, the appearance of OSA can be quite variable. Commonly observed features include cortical lysis, soft tissue extension with soft tissue swelling and new bone (tumor or reactive) formation. Primary lesions are typically monostotic. Based on signalment (patient-specific factors such as breed, sex, age, etc.), history, physical examination and radiographic findings, a presumptive diagnosis of OSA may be made. Cytology may support a tentative diagnosis. In most cases, a definitive diagnosis is made via histopathology. Bone biopsy is performed prior to pursuing treatment. Samples can be obtained via open incisional, closed-needle, or trephine biopsy techniques. In some cases, repeated biopsy attempts yield “reactive bone,” making it very difficult to obtain the diagnosis preoperatively. Histopathology is performed after tumor removal (amputation or limb sparing) to confirm the preoperative diagnosis. Figure 1 summarizes the elements of the diagnostic work-up of OSA in canines.


Figure 1.

Examples of canine osteosarcoma. (A) and (B) Typical radiographic findings including ill-defined lesions with aggressive periosteal reaction and tumor matrix ossification. (C) and (D) High-grade, highly pleomorphic cells with surrounding osteoid.

5. Diagnostic work-up: metastatic disease

Approximately 10% of dogs will have gross evidence of metastatic disease at diagnosis. Fewer than 15% of cases have detectable pulmonary metastasis and less than 8% have metastasis to other musculoskeletal sites. Three view thoracic radiographs are recommended to evaluate for pulmonary metastasis; however, metastases cannot be detected radiographically until the nodules are 6–8 mm in diameter. This underscores the belief that in dogs, as with humans, the presence of metastatic disease on presentation is likely underappreciated. Advanced imaging (e.g., CT, MRI, PET/CT) may be used for patient staging [32, 33]. A thorough orthopedic examination with palpation of long bones and the accessible axial skeleton is necessary to evaluate for sites of bony metastasis. Bone survey radiographs, including lateral views of all bones in the body and a ventrodorsal projection of the pelvis, have been useful in detecting second skeletal sites of OSA [34]. Whereas whole-body bone scans are standard in human medicine, there are conflicting reports on the utility of nuclear scintigraphy for clinical staging of dogs with OSA [3539]. It can be useful for detection and localization of bone metastasis in dogs presenting for vague lameness or signs of back pain. Although it is a very sensitive imaging modality, it is not specific for identifying skeletal tumors.

6. Prognostic factors

Tumor size, determined as an actual tumor volume or the percentage of bone length affected by tumor, has been found to be a prognostic indicator in dogs. Large tumors have been found to have a poorer prognosis [11, 27, 40, 41]. Tumor location is also a prognostic factor. In general, tumors of the mandible and scapula carry the most favorable prognosis. Other than the mandible and scapula, tumors of the axial skeleton carry a poor prognosis with survival times often less than 6 months. Tumors of the appendicular skeleton are intermediate in prognosis. Specifically, tumors of the appendicular skeleton (radius, ulna, humerus, femur and tibia) are associated with a median survival time of 1 year when treated with aggressive surgery and chemotherapy [21]. Median disease-free intervals (DFIs) and disease- free survival (DFS) times for skull OSA are 191 days and 204 days, respectively. In one study, dogs with mandibular OSA treated with mandibulectomy alone had a 1-year survival rate of 71% [18]. Dogs with maxillary OSA have been found to have a median survival time of 5 months following maxillectomy [42, 43]. A study of orbital OSA reported long-term survival following complete surgical excision [44]. Median survival time for dogs with rib OSA is reported to be 3 months for cases treated with rib resection alone and 8 months for cases treated with resection and adjuvant chemotherapy [4548]. DFI and median survival time in dogs with scapula OSA was 210 days and 246 days, respectively, with the use of adjuvant chemotherapy increasing DFI and survival time [49]. Survival time of dogs with OSA distal to the antebrachiocarpal (equivalent of human wrist) or tarsocrural joints (human ankle) has a median survival time of 466 days, which is longer than the survival time of dogs with OSA of more common appendicular sites. However, OSA of these sites is aggressive, with a high potential for metastasis [50]. Extraskeletal OSA has an aggressive systemic behavior with a high metastatic rate, with short median survival times ranging from 1 month to 5 months [27, 28].

As in humans, elevated alkaline phosphatase (ALP) has been associated with a poorer prognosis for dogs with appendicular OSA [27, 5154]. A preoperative elevation of either serum ALP or the bone isoenzyme of ALP (>110 U/L or 23 U/L, respectively) is associated with a shorter disease-free interval and survival. Dogs that have elevated preoperative values that do not return to normal within 40 days following surgical removal of the primary tumor also develop earlier metastasis. At least one study has suggested that tumor grade, characterized by degree of necrosis, mitotic rate and cell differentiation, is also highly prognostic, with higher grade tumors having shorter survival times and disease-free intervals [55].

7. Treatment

Cure is achieved in fewer than 15% of dogs diagnosed with OSA. For the most effective management, multimodality therapy is required to address both local and systemic disease. Amputation, limb-sparing surgeries, as well as nonsurgical techniques, such as stereotactic radiation therapy (SRT), are highly effective for management of local disease (contrary to management of OSA in humans, in which radiation therapy is rarely used). Amputation is the standard local treatment for appendicular OSA and readily allows for adequate surgical margins. It is well tolerated in dogs and offers significant improvement in pain relief and survival relative to palliative treatment. Pelvic tumors are treated with amputation and hemipelvectomy and these patients generally have good levels of function. Rib tumors are treated with thoracic wall resection; mandibular tumors are treated with hemimandibulectomy and maxillary tumors are treated with partial maxillectomy and/or orbitectomy. Limb salvage surgery, most commonly using bone allografts or metal endoprostheses, can be performed in some dogs with appendicular OSA. The most suitable patients for limb salvage are dogs with tumors in the distal radius or ulna [15], but tumors of the scapula, diaphyseal radius and ulna, metacarpus, metatarsus, diaphyseal humerus, femur and tibia and distal tibia have also been treated with limb salvage surgery [21]. Limb function following limb salvage surgery is found to be good to excellent in most dogs and survival is not adversely affected by removing the primary tumor with marginal resection. Intraoperative radiation therapy and extracorporeal intraoperative RT (IORT) have also been utilized in a small number of canine OSA patients. Stereotactic radiation therapy (SRT) is a nonsurgical alternative method which is used on an increasingly common basis for facilitating canine limb salvage. This technique can provide adequate local control of disease in the context of a life expectancy for dogs that is almost always shorter than 2 years, even with systemic therapy.

Although amputation and limb-sparing surgeries, as well as nonsurgical techniques such as SRT, have proved highly effective for management of local disease, the ability to control the progression of OSA metastases remains a clinical challenge. Systemic chemotherapy is the essential component for management of OSA metastases. Protocols that have shown significant improvement in survival include doxorubicin, cisplatin and carboplatin, with medial survival times of approximately 1 year [18, 40, 56, 57]. Lobaplatin has also been used but provides a median survival time of 7 months [21]. No survival advantage has been found when using combination chemotherapy. Despite the aggressive treatment approach, more than 50% of dogs do not live beyond 1 year postamputation and 90% die of disease by 2 years [15]. Further research is needed for discovering effective new combination therapies for improving the long-term prognosis of canine OSA.

8. The dog as a “model” of osteosarcoma

A number of animal models of OSA exist; however, the reliance upon mouse models of OSA has limitations. The canine “model” of spontaneously occurring OSA offers several advantages over non-spontaneous models. It is often described as a “model” (emphasis on quotation marks) because for these patients and their owners; it is not a model at all—they are being treated for a pathologic condition. Naturally occurring OSA in dogs better represents the biological complexity and heterogeneity of the disease than traditional rodent models and, as such, shares a wide variety of epidemiologic and clinical features with human OSA [58]. Genetically, there are far more similarities between dogs and humans than between rodents and humans [59]. Pet dogs share a living environment with humans and are subsequently exposed to many of the same environmental risk factors that contribute to the occurrence of solid tumors in humans. Additionally, tumors in canines occur in the context of intact immune systems, allowing for a better representation of immunologic influence on cancer progression and spread [4]. These tumors are further characterized by high levels of heterogeneity between individuals and between tumors; this heterogeneity is often lacking in traditional models. They also demonstrate the capacity for the development of local recurrence, resistance to treatment and distant metastases, typically to the lungs, just as these tumors do in human patients. Table 1 summarizes the key similarities and differences between human and canine osteosarcoma. Figure 2 summarizes the diagnostic work-up for human osteosarcoma.

Incidence>10,000 cases per year<1000 cases per year
Median age of onsetMiddle-aged to older dogs
Peak onset 7–9 years
Second small peak at 18–24 months
Bimodal disease with peak onset 10–14 years
Second peak at >65 years
Race/breedLarge or giant breed
Increased height and weight
Increased risk in Saint Bernard, Great Dane, Irish setter, Doberman pinscher, Rottweiler, German shepherd, golden retriever
Slightly more common in African Americans and Hispanics
Primary site75% appendicular skeleton
Metaphyseal region of long bones
Distal radius > proximal humerus > distal ulna > distal femur > proximal tibia > distal tibia > diaphyseal ulna
90% appendicular skeleton
Metaphyseal region of long bones
Distal femur > proximal tibia > proximal humerus
Metastatic sites10% of cases with metastasis at diagnosis
Lung > bone > soft tissues
20% of cases with metastasis at diagnosis
Lung > bone > soft tissues
Molecular and genetic playersp53
Limb-sparing techniques
Adjuvant chemotherapy
Neoadjuvant chemotherapy
Limb-sparing techniques
Amputation (rare)
Survival~50% survival at 1 year with chemotherapy, 10% at 2 years60–80% survival at 5 years with chemotherapy
Prognostic factorsTumor size
Tumor location (distal more favorable than proximal)
Proximal humeral location
Metastasis at diagnosis
Serum alkaline phosphatase
Response to chemotherapy
Tumor size
Tumor location (distal more favorable than proximal)
Proximal humeral location
Metastasis at diagnosis
Serum alkaline phosphatase
Serum lactate dehydrogenase
Response to chemotherapy

Table 1.

Comparison of human and canine osteosarcoma.


Figure 2.

(A) Gross histology demonstrating a destructive osseous lesion with an associated soft tissue mass, (B) high-grade cellular lesion with a trabecular pattern and osteoid production, (C) radiographic findings demonstrating increased sclerosis, with a large periosteal reaction, and (D) MRI images demonstrating cortical destruction and a large soft tissue mass (images collected with permission) [60].

An important power nestled in the study of canine OSA lies in the concept of linkage disequilibrium and the breed structure of canines [61]. Approximately two centuries ago, the practice of selecting canines for certain morphological and behavioral traits grew in popularity, paving the path for modern dog breeds. An unforeseen side effect of breeding was the selection of certain “founder” mutations linked to certain breed-specific traits and diseases. This is seen today in the form of certain breed showing a predilection for species-specific diseases, with the practical result of this “founder” effect being an overall loss of heterogeneity among genes and diseases. Linkage equilibrium is present to a significantly higher degree in canines as compared to humans, making individual breed analysis a strong tool for broad-spectrum genetic mapping [61, 62]. When comparing similar traits between breeds, fine mapping may also be performed, thus making canine models of spontaneously occurring OSA a powerful model for identifying the genetic origins of this disease.

Perhaps, the greatest shortcoming from studying human OSA is the relatively low incidence of the disease. Therapeutics must be evaluated over the course of several years and studies face the challenge of reaching statistically significant power. A solution to this particular challenge is available in the form of cross-species analysis of canine OSA. Canine OSA has an incidence on the order of at least tenfold greater than human OSA [62]. In addition to this significantly larger patient population, dogs also have a shorter life span with faster progression of disease and a shorter period of survival relative to humans [1]. Thus, the collection of data and the evaluation of novel treatments may be carried out more rapidly in dogs than in humans. Although the more rapid life course in dogs is not surprising, as life spans generally decrease along with species size, the reason for poorer outcomes in dogs with OSA is more puzzling. Whether this represents a fundamental difference in treatment (systemic therapy in dogs is relatively less aggressive on a dosage basis) or in disease, biology is not known. Whatever the reason for the difference in survival, the combination of increased patient numbers, time-compressed progression of disease, genetic similarities and spontaneous tumor origin within a natural environmental and immunologic background renders canine OSA an ideal model in which to study the disease.

9. Elucidating the genetic origins of osteosarcoma

The genetic and molecular origins of OSA remain poorly understood. Any given tumor may demonstrate tremendous genetic variation and complexity, characterized by abnormal genetic structural and copy number changes, irregular karyotypes and gross aneuploidy, making elucidation of common pathways more difficult [31, 63, 64]. Dogs with spontaneously occurring OSA present a unique alternative to humans for identifying conserved genetic drivers of OSA. The dog genome was mapped a decade ago and is publicly accessible via the CanFam genome browser, making genetic comparisons with the humans relatively simple [59, 65, 66]. Early genetic studies have demonstrated that canine and human OSAs are virtually indistinguishable. A study by Paoloni et al. used parallel oligonucleotide arrays to compare OSA expression signatures between human and canine samples; interestingly, hierarchical clustering could not segregate the samples by species of origin [67]. Studies such as this demonstrate the tremendous capacity for genomic analysis using comparative oncology; a number of shared molecular targets have been identified using this comparative analysis between canines and humans, including RTK MET, STAT3 and others [6872].

The breeding of dogs has created artificially selected and refined gene pools. Some breeds of dog, such as Rottweilers and Irish wolfhounds, have also developed a reduced intra-breed genetic diversity and disproportionately higher rates of OSA [17, 73]. This presents an opportunity to examine genetic risk factors for the development of OSA. One study examining the Scottish deerhound used whole-genome mapping to find a linkage for the OSA phenotype. A novel locus was identified on chromosome 34 in a region homologous to human chromosome 3q26, demonstrating a potential genetic basis for the disease in both canines and humans [74]. Another study examined the molecular profiles of dogs with OSA in order to identify subtypes and stratify this disease based on gene expression profiling and its biological behavior. This study was able to identify groupings associated with G2/M transitions and DNA damage checkpoints that correlated with biological activity; additionally, these groupings translated to orthologous human molecular subtypes with similar biological activity [75]. Finally, Angstadt et al. used high-resolution oligonucleotide assays to identify common genome-wide copy number aberrations in both human and canine samples of OSA [76]. Their study reaffirmed a number of known aberrant genes and identified several new genes in regions of instability pointing toward possible players in the genetic origin of OSA. Taken as a whole, these studies demonstrate the capacity for genome-wide analysis and comparisons between dogs and humans to identify possible genetic precursors and drivers of OSA.

Numerous somatic genetic similarities have been identified as a commonality between human and canine OSA, which may help identify new and important insights into OSA biology. p53 and RB1, tumor suppressor genes, are possibly two of the best-known and well-described genetic aberrations in both human and canine OSA. With p53, genetic abnormalities in canine OSA are typically the result of missense mutations, which result in an overexpression of this gene and are present in 41–67% of primary OSA tumors [29, 30, 77]. While p53 is often mutated in primary cases of human OSA, it is found at a much lower rate, with only about 20% of cases showing this abnormality [78]; unlike canine OSA, mutations in the p53 gene in humans are often point mutations [30]. RB1 is a genetic abnormality that is common in human forms of OSA, estimated to be present in 30–75% of cases [79]. While initial studies questioned the putative role of RB1, more recent studies indicate that mutations of this gene are present in 29% of cases of OSA, typically resulting in a reduction or complete absence of the gene product [31, 80]. PTEN is another tumor suppressor gene that has been implicated in both human and canine OSA. Early findings in canine OSA cell lines implicated PTENdeletions and a reduction in gene expression in the development of this cancer [29]; this was confirmed using a comparative genomic hybridization (CGH) genomic analysis in primary canine OSA, which found that PTEN mutations were present in 30–42% of tumors examined [31, 76]. Human studies have similarly identified PTEN as a common mutation present in primary cases of OSA [81].

10. Advances in surgical technique and adjunct therapy

10.1. Surgical and medical therapy for canine osteosarcoma parallels human therapy

There are a number of similarities in systemic therapy and surgical management between human and canine OSA. In both patient populations, en bloc surgical resection, in combination with chemotherapy, is the mainstay of treatment; the addition of either neoadjuvant or adjuvant chemotherapy has further improved survival rates and is now also considered a part of standard of care. Most dogs are treated with adjuvant—rather than neoadjuvant—chemotherapy, as there is less data in dogs regarding the prognostic value of histopathologic response to therapy.

Pioneering of limb-sparing techniques in the surgical treatment of OSA was initially conducted in dogs. One of the early studies of the potential role of limb salvage in canine patients with OSA was conducted by LaRue et al. [82]. This study found that limb salvage in addition to multimodality therapy could represent a viable alternative to amputation in the management of certain patients. A subsequent study by Withrow et al. [83] similarly studied the role of limb salvage surgery as an option in the management of OSA. Forty-nine dogs with limb-sparing resection for OSA of the extremity were followed and stratified by the addition of chemotherapy or chemotherapy with radiation therapy. As in humans, outcomes were significantly linked to percent necrosis, which was improved by a combination of chemotherapy with radiation therapy. Higher rates of tumor necrosis resulted in higher overall survival and better outcomes. The breadth of this data is not as extensive in dogs as it is in humans and the paradigm of chemotherapy/surgery/chemotherapy has not become normative in dogs. Despite similarities in overall survival between amputation and limb-sparing surgery, a significant issue with limb salvage in both canines and humans has been the inadequacy of functional outcomes and the prevalence of postoperative complications. A study by Kuntz et al. [84] examined 17 patients with OSA of the proximal humerus undergoing limb salvage surgery using frozen humeral allografts. As expected, completeness of margins significantly impacted the overall rates of survival, with incomplete margins resulting in an eightfold higher rate of distant metastases. As in humans, when comparing limb salvage with amputation, there was no statistically significant difference in overall survival. However, postoperative functional outcomes and rates of complications were deemed to be unacceptable. Only 12% of patients had good or excellent outcomes with many of the dogs treated with limb salvage suffering from biomechanical failure of their mechanical constructs and 41% of patients receiving limb salvage surgery required conversion to amputation. A retrospective study of human OSA by Rougraff et al. found limb salvage demonstrated similar outcomes with respect to disease-free survival and overall survival when local control via limb salvage is compared to local control via amputation [85]. This has similarly been borne out in canine OSA [18].

The addition of chemotherapy to the management of OSA has dramatically improved outcomes and become a mainstay of treatment for both dogs and humans with OSA. The overall survival of dogs treated with amputation is significantly improved by the addition of chemotherapy. In addition to the previously mentioned studies conducted by LaRue et al. and Withrow et al. [82, 83], 30 dogs with appendicular OSA were evaluated in a study evaluating overall survival rates when treated with and without the addition of cisplatin [86]. Mean survival time was 190 days for patients treated with amputation alone; mean survival time improved to 315 days with the addition of cisplatin. Similar results were found in a study by Berg et al. [56], which examined 22 dogs with appendicular OSA treated with surgical resection with and without the addition of cisplatin. They found a statistically significant increase in survival with the addition cisplatin to surgical management. Interestingly, there was no survival difference between chemotherapy in addition to amputation and limb-sparing surgery, though the cohort numbers were likely too low to draw significant results in this regard. Thesis parallels in the medical and surgical management of OSA across species contribute to canine OSA being particularly well suited in comparison with humans undergoing similar treatment [8789].

10.2. Novel therapeutics and immunotherapies

Canine models have been an important avenue by which to examine novel therapeutic strategies for OSA. With the advent of intra-arterial chemotherapy, randomized control trials were conducted in dogs with spontaneously occurring OSA to evaluate the safety, efficacy and feasibility of this method of delivery in the treatment of OSA [82]. With the advent of intra-arterial chemotherapy, randomized control trials were conducted in canines with spontaneously occurring OSA to evaluate the safety, efficacy and feasibility of this method of delivery in the treatment of OSA [83]. Similarly, dose escalation studies conducted in canines with OSA have allowed for optimization of chemotherapeutic drug delivery in humans. In a study by Paoloni et al., a phase I dose-escalation study was conducted with rapamycin delivery in canines with the simultaneous collection of multiple pre- and posttreatment biopsies and whole blood sampling to establish efficacy and ideal drug pharmacokinetic time points, data that would have been more challenging to collect in human patients [90]. These insights were translated into a human clinical trial of rapamycin, allowing for a better understanding of dosing and efficacy of the drug [91, 92]. These studies allowed optimization of the dose and delivery of chemotherapy in humans with OSA while allowing for earlier screening of treatments that may have a less than favorable therapeutic index before being tested in humans [93, 94]. Beyond cytotoxicity and optimization studies, canines with OSA have also served as the ideal models for identifying and evaluating novel therapeutics.

Early insights into the role of the immune system in OSA disease progression came about by happenstance while studying canine OSA. While studying outcomes in canines undergoing the combination of limb salvage and chemotherapy, Lascelles et al. found that postoperative infection significantly improved survival [95]. These findings were also recapitulated in humans, as a study by Jeys et al. demonstrated; humans with deep infection following limb salvage for OSA experienced a 35% increase in overall survival rate [96, 97]. These survival benefits were hypothesized to be related to an upregulation in the natural antitumoral activity of the host immune system. This has inspired new investigations into the specific role of the immune system in OSA and the ways in which cancer suppresses the natural immune response. Analysis of canines with and without OSA has identified myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) that may play a role in suppression of the natural antitumor response of the host [98, 99]. These cells normally function to prevent the antitumoral response from overaction and resultant autoimmunity. Suppressing these cells has been hypothesized as a means of promoting the antitumoral response to improve outcomes in OSA. Although some have associated increased ratios of Tregs with poorer outcomes in canine OSA [100], there remain questions as to whether Treg levels are actually different from healthy controls [99]. MDSCs have also been found to be overrepresented in canine OSA, as demonstrated in two studies by Sherger et al. and Goulart et al. [101, 102]. Similar to Tregs, the role of MDSCs in OSA remains unclear, though increased monocyte counts have been associated with worse outcomes and decreased rates of DFS [103, 104]. Despite the ambiguity surrounding their potential role in OSA progression, Tregs and MDSCs highlight the potential for immune targets in the treatment of OSA.

Immunotherapy for sarcoma is an exciting new field of cancer treatment currently being investigated in both humans and canines. One such agent, liposomal muramyl tripeptide phosphatidylethanolamine (L-MTP-PE), had its first success demonstrated in dogs with spontaneously occurring OSA. This synthetic molecule is an analog of a bacterial cell wall component and a potent activator of monocytes/macrophages. It can be incorporated into liposomes and has been shown to selectively induce monocytes to kill tumor cells [105]. In a study of 40 dogs receiving standard therapy with surgery and cisplatin, canines were randomized to receive the addition of either L-MTP-PE or a placebo. Patients receiving L-MTP-PE had significantly better rates of overall survival as compared to placebo [106]. This study has translated to human pediatric patients with OSA as well, with results indicating L-MTP-PE as a possible adjunct in the repertoire of treatments available for OSA [107, 108].

While immunotherapy is an exciting realm of novel therapeutics in canines with OSA, the canine model is equally beneficial in evaluating the safety and efficacy of a variety of novel therapeutics and novel applications of existing therapies [109]. One such application is the use of aerosolized delivery of chemotherapeutics for pulmonary metastases, which has made significant progress thanks to research conducted in dogs with OSA. A translational study by Rodriguez et al. examined the effect of aerosol delivery of gemcitabine to pulmonary metastasis in dogs with OSA [110]. This study demonstrated an increased in Fas expression and increased rates of apoptosis in pulmonary metastases. Cross-species drug development using canines as a model for human OSA has also been suggested for targets including genetic abnormalities (TP53 and murine double minute-2), growth factors (c-MET and mTOR), angiogenesis (VEGF and HIF-1a) and metastasis (membrane-type-1 matrix metalloproteinase) [2354, 90, 111116].

11. Conclusion: challenges and limitations

OSA remains a challenging diagnosis with little change in the prognosis for several decades. Recognizing the utility of studying animals with diseases shared by humans, Rudolf Virchow stated in the mid-nineteenth century, “Between animal and human medicine there is no dividing line, nor should there be.” Yet despite a desperate need to investigate OSA in greater numbers and scope, dogs with naturally occurring OSA were not seriously studied until the late twentieth century. Man’s best friend provides us an opportunity to study one of our most dreaded diagnoses in larger numbers than we could ever hope to study in humans alone. With similar disease features and treatment algorithms, research may be carried out in dogs in a more facile manner than in humans. Continuing to expand our understanding and awareness of canine, OSA will be a critical step in developing novel and better therapeutic strategies.

Several challenges do remain [93]. While canine models show an accelerated disease progression as compared to humans, this timeline is still significantly longer than murine models. While funding for mouse models of cancer is widespread, funding for the investigation of canine cancer remains sparse. Some novel therapies, such as species-specific antibodies and proteins, may not translate from canines to humans and vice versa. Finally, regulatory oversight and ethical care mandate that some study designs are simply not feasible in pets. Despite these limitations, this review demonstrates that canines are an ideal—and underutilized—model to deepen our understanding of osteosarcoma and to translate exciting developments from the laboratory into the clinic.


1 - Withrow SJ, Powers BE, Straw RC, Wilkins RM. Comparative aspects of osteosarcoma. Dog versus man. Clin Orthop Relat Res. 1991(270):159-68.
2 - Mirabello L, Troisi RJ, Savage SA. Osteosarcoma incidence and survival rates from 1973 to 2004: data from the Surveillance, Epidemiology, and End Results Program. Cancer. 2009;115(7):1531-43.
3 - Spodnick GJ, Berg J, Rand WM, Schelling SH, Couto G, Harvey HJ, et al. Prognosis for dogs with appendicular osteosarcoma treated by amputation alone: 162 cases (1978–1988). J Am Vet Med Assoc. 1992;200(7):995-9.
4 - Khanna C, Lindblad-Toh K, Vail D, London C, Bergman P, Barber L, et al. The dog as a cancer model. Nature Biotechnol. 2006;24(9):1065-6.
5 - Brodey RS, Mc GJ, Reynolds H. A clinical and radiological study of canine bone neoplasms. I. J Am Vet Med Assoc. 1959;134(2):53-71.
6 - Brodey RS, Riser WH. Canine osteosarcoma. A clinicopathologic study of 194 cases. Clin Orthop Relat Res. 1969;62:54-64.
7 - Brodey RS, Sauer RM, Medway W. Canine bone neoplasms. J Am Vet Med Assoc. 1963;143:471-95.
8 - Dorfman SK, Hurvitz AI, Patnaik AK. Primary and secondary bone tumours in the dog. J Small Anim Pract. 1977;18(5):313-26.
9 - Ling G, Morgan J, Pool R. Primary bone rumors in the dog: a combined clinical, radiographic, and histologic approach to early diagnosis. J Am Vet Med Assoc. 1974;165(1):55.
10 - Priester WA, McKay FW. The occurrence of tumors in domestic animals. Natl Cancer Inst Monogr. 1980(54):1-210.
11 - Misdorp W, Hart A. Some prognostic and epidemiologic factors in canine osteosarcoma. J Natl Cancer Inst. 1979;62(3):537-45.
12 - Feeney DA, Johnston GR, Grindem CB, Toombs JP, Caywood DD, Hanlon GF. Malignant neoplasia of canine ribs: clinical, radiographic, and pathologic findings. J Am Vet Med Assoc. 1982;180(8):927-33.
13 - Heyman SJ, Diefenderfer DL, Goldschmidt MH, Newton CD. Canine axial skeletal osteosarcoma. A retrospective study of 116 cases (1986 to 1989). Vet Surg. 1992;21(4):304-10.
14 - Misdorp W. Skeletal osteosarcoma. Animal model: canine osteosarcoma. Am J Pathol. 1980;98(1):285-8.
15 - Ehrhart NP, Ryan SD, Fan TM. Tumors of the skeletal system. Small Anim Clin Oncol, 5th ed. 2013:463-503.
16 - Alexander JW, Patton CS. Primary tumors of the skeletal system. Vet Clin North Am Small Anim Pract. 1983;13(1):181-95.
17 - Ru G, Terracini B, Glickman LT. Host related risk factors for canine osteosarcoma. Vet J. 1998;156(1):31-9.
18 - Straw RC, Withrow SJ. Limb-sparing surgery versus amputation for dogs with bone tumors. Vet Clin North Am Small Anim Pract. 1996;26(1):135-43.
19 - Wolke RE, Nielsen SW. Site incidence of canine osteosarcoma. J Small Anim Pract. 1966;7(7):489-92.
20 - Fenger JM, London CA, Kisseberth WC. Canine osteosarcoma: a naturally occurring disease to inform pediatric oncology. ILAR J. 2014;55(1):69-85.
21 - Kuntz CA. Appendix B: canine osteosarcoma, In: Malawer MM and Sugarbaker PH (eds). Muscoloskeletal cancer surgery – treatment of sarcomas and allied diseases. Springer Publishers. 2001:603-7.
22 - Patnaik AK. Canine extraskeletal osteosarcoma and chondrosarcoma: a clinicopathologic study of 14 cases. Vet Pathol. 1990;27(1):46-55.
23 - Thamm DH, O'Brien MG, Vail DM. Serum vascular endothelial growth factor concentrations and postsurgical outcome in dogs with osteosarcoma. Vet Comp Oncol. 2008;6(2):126-32.
24 - Salm R, Mayes SE. Retroperitoneal osteosarcoma in a dog. Vet Rec. 1969;85(23):651-3.
25 - Ringenberg MA, Neitzel LE, Zachary JF. Meningeal osteosarcoma in a dog. Vet Pathol. 2000;37(6):653-5.
26 - Bech-Nielsen S, Haskins ME, Reif JS, Brodey RS, Patterson DF, Spielman R. Frequency of osteosarcoma among first-degree relatives of St. Bernard dogs. J Natl Cancer Inst. 1978;60(2):349-53.
27 - Kuntz CA, Dernell WS, Powers BE, Withrow S. Extraskeletal osteosarcomas in dogs: 14 cases. J Am Anim Hosp Assoc. 1998;34(1):26-30.
28 - Langenbach A, Anderson M, Dambach D, Sorenmo K, Shofer F. Extraskeletal osteosarcomas in dogs: a retrospective study of 169 cases (1986–1996). J Am Anim Hosp Assoc. 1998;34(2):113-20.
29 - Levine RA, Fleischli MA. Inactivation of p53 and retinoblastoma family pathways in canine osteosarcoma cell lines. Vet Pathol. 2000;37(1):54-61.
30 - Kirpensteijn J, Kik M, Teske E, Rutteman GR. TP53 gene mutations in canine osteosarcoma. Vet Surg. 2008;37(5):454-60.
31 - Thomas R, Wang HJ, Tsai PC, Langford CF, Fosmire SP, Jubala CM, et al. Influence of genetic background on tumor karyotypes: evidence for breed-associated cytogenetic aberrations in canine appendicular osteosarcoma. Chromosome Res. 2009;17(3):365-77.
32 - Picci P, Vanel D, Briccoli A, Talle K, Haakenaasen U, Malaguti C, et al. Computed tomography of pulmonary metastases from osteosarcoma: the less poor technique. A study of 51 patients with histological correlation. Ann Oncol. 2001;12(11):1601-4.
33 - Waters DJ, Coakley FV, Cohen MD, Davis MM, Karmazyn B, Gonin R, et al. The detection of pulmonary metastases by helical CT: a clinicopathologic study in dogs. J Comput Assist Tomogr. 1998;22(2):235-40.
34 - LaRue SM, Withrow SJ, Wrigley RH. Radiographic bone surveys in the evaluation of primary bone tumors in dogs. J Am Vet Med Assoc. 1986;188(5):514-6.
35 - Berg J, Lamb CR, O'Callaghan MW. Bone scintigraphy in the initial evaluation of dogs with primary bone tumors. J Am Vet Med Assoc. 1990;196(6):917-20.
36 - Hahn KA, Hurd C, Cantwell HD. Single-phase methylene diphosphate bone scintigraphy in the diagnostic evaluation of dogs with osteosarcoma. J Am Vet Med Assoc. 1990;196(9):1483-6.
37 - Jankowski M, Steyn P, Lana S, Dernell W, Blom C, Uhrig J, et al. Nuclear scanning with 99mTc‐HDP for the initial evaluation of osseous metastasis in canine osteosarcoma. Vet Comp Oncol. 2003;1(3):152-8.
38 - Lamb C. Bone scintigraphy in small animals. J Am Vet Med Assoc. 1987;191(12):1616.
39 - Parchman MB, Flanders JA, Erb HN, Wallace R, Kallfelz FA. Nuclear medical bone imaging and targeted radiography for evaluation of skeletal neoplasms in 23 dogs. Vet Surg. 1990;18(6):454-8.
40 - Bergman PJ, MacEwen EG, Kurzman ID, Henry CJ, Hammer AS, Knapp DW, et al. Amputation and carboplatin for treatment of dogs with osteosarcoma: 48 cases (1991 to 1993). J Vet Intern Med. 1996;10(2):76-81.
41 - Cho WH, Song WS, Jeon D-G, Kong C-B, Kim MS, Lee JA, et al. Differential presentations, clinical courses, and survivals of osteosarcomas of the proximal humerus over other extremity locations. Annal Surg Oncol. 2010;17(3):702-8.
42 - Schwarz P, Withrow S, Curtis C, Powers B, Straw R. Partial maxillary resection as a treatment for oral cancer in 61 dogs. J Am Anim Hosp Assoc (USA). 1991.
43 - Wallace J, Matthiesen DT, Patnaik AK. Hemimaxillectomy for the treatment of oral tumors in 69 dogs. Vet Surg. 1992;21(5):337-41.
44 - Hendrix D, Gelatt K. Diagnosis, treatment and outcome of orbital neoplasia in dogs: a retrospective study of 44 cases. J Small Anim Pract. 2000;41(3):105-8.
45 - Baines SJ, Lewis S, White RA. Primary thoracic wall tumours of mesenchymal origin in dogs: a retrospective study of 46 cases. Vet Rec. 2002;150(11):335-9.
46 - Matthiesen DT, Clark GN, Orsher RJ, Pardo AO, Glennon J, Patnaik AK. En bloc resection of primary rib tumors in 40 dogs. Vet Surg. 1992;21(3):201-4.
47 - Montgomery R, Henderson R, Powers R, Withrow S, Straw R, Freund J, et al. Retrospective study of 26 primary tumors of the osseous thoracic wall in dogs. J Am Anim Hosp Assoc (USA). 1993: (29) 68–72.
48 - Pirkey-Ehrhart N, Withrow SJ, Straw RC, Ehrhart EJ, Page RL, Hottinger HL, et al. Primary rib tumors in 54 dogs. J Am Anim Hosp Assoc. 1994;31(1):65-9.
49 - Montinaro V, Boston SE, Buracco P, Culp WT, Romanelli G, Straw R, et al. Clinical outcome of 42 dogs with scapular tumors treated by scapulectomy: A Veterinary Society of Surgical Oncology (VSSO) retrospective study (1995–2010). Vet Surg. 2013;42(8):943-50.
50 - Gamblin RM, Straw RC, Powers BE, Park RD, Bunge MM, Withrow SJ. Primary osteosarcoma distal to the antebrachiocarpal and tarsocrural joints in nine dogs (1980–1992). J Am Anim Hosp Assoc. 1994;31(1):86-91.
51 - Ehrhart N, Dernell W, Hoffmann W, Weigel R, Powers B, Withrow S. Prognostic importance of alkaline phosphatase activity in serum from dogs with appendicular osteosarcoma: 75 cases (1990–1996). J Am Vet Med Assoc. 1998;213(7):1002-6.
52 - Hillers KR, Dernell WS, Lafferty MH, Withrow SJ, Lana SE. Incidence and prognostic importance of lymph node metastases in dogs with appendicular osteosarcoma: 228 cases (1986–2003). J Am Vet Med Assoc. 2005;226(8):1364-7.
53 - Garzotto CK, Berg J, Hoffmann WE, Rand WM. Prognostic significance of serum alkaline phosphatase activity in canine appendicular osteosarcoma. J Vet Intern Med. 2000;14(6):587-92.
54 - Moore AS, Dernell WS, Ogilvie GK, Kristal O, Elmslie R, Kitchell B, et al. Doxorubicin and BAY 12-9566 for the treatment of osteosarcoma in dogs: a randomized, double-blind, placebo-controlled study. J Vet Intern Med. 2007;21(4):783-90.
55 - Kirpensteijn J, Kik M, Rutteman G, Teske E. Prognostic significance of a new histologic grading system for canine osteosarcoma. Vet Pathol Online. 2002;39(2):240-6.
56 - Berg J, Weinstein MJ, Schelling SH, Rand WM. Treatment of dogs with osteosarcoma by administration of cisplatin after amputation or limb-sparing surgery: 22 cases (1987–1990). J Am Vet Med Assoc. 1992;200(12):2005-8.
57 - Maulding G, Matus R, Withrow S, Patnaik A. Canine osteosarcoma. Treatment by amputation and adjuvant chemotherapy using doxorubicin and cisplatin. J Vet Inter Med. 1988;2(4):177-80.
58 - Pinho SS, Carvalho S, Cabral J, Reis CA, Gartner F. Canine tumors: a spontaneous animal model of human carcinogenesis. Transl Res. 2012;159(3):165-72.
59 - Lindblad-Toh K, Wade CM, Mikkelsen TS, Karlsson EK, Jaffe DB, Kamal M, et al. Genome sequence, comparative analysis and haplotype structure of the domestic dog. Nature. 2005;438(7069):803-19.
60 - Lazarides A, Erdmann D, Powers D, Eward W. Custom facial reconstruction for osteosarcoma of the jaw. J Oral Maxillofac Surg. 2014;72(11):2375 e1-10.
61 - Parker HG, Shearin AL, Ostrander EA. Man's best friend becomes biology's best in show: genome analyses in the domestic dog. Annu Rev Genet. 2010;44:309-36.
62 - Rowell JL, McCarthy DO, Alvarez CE. Dog models of naturally occurring cancer. Trends Mol Med. 2011;17(7):380-8.
63 - Maeda J, Yurkon CR, Fujisawa H, Kaneko M, Genet SC, Roybal EJ, et al. Genomic instability and telomere fusion of canine osteosarcoma cells. PLoS One. 2012;7(8):e43355.
64 - Selvarajah S, Yoshimoto M, Ludkovski O, Park PC, Bayani J, Thorner P, et al. Genomic signatures of chromosomal instability and osteosarcoma progression detected by high resolution array CGH and interphase FISH. Cytogenet Genome Res. 2008;122(1):5-15.
65 - Sutter NB, Ostrander EA. Dog star rising: the canine genetic system. Nat Rev Genet. 2004;5(12):900-10.
66 - Ostrander EA, Comstock KE. The domestic dog genome. Curr Biol. 2004;14(3):R98-9.
67 - Paoloni M, Davis S, Lana S, Withrow S, Sangiorgi L, Picci P, et al. Canine tumor cross-species genomics uncovers targets linked to osteosarcoma progression. BMC Genom. 2009;10:625.
68 - Mintz MB, Sowers R, Brown KM, Hilmer SC, Mazza B, Huvos AG, et al. An expression signature classifies chemotherapy-resistant pediatric osteosarcoma. Cancer Res. 2005;65(5):1748-54.
69 - Fossey SL, Liao AT, McCleese JK, Bear MD, Lin J, Li PK, et al. Characterization of STAT3 activation and expression in canine and human osteosarcoma. BMC Cancer. 2009;9:81.
70 - Liao AT, McMahon M, London C. Characterization, expression and function of c-Met in canine spontaneous cancers. Vet Comp Oncol. 2005;3(2):61-72.
71 - MacEwen EG, Kutzke J, Carew J, Pastor J, Schmidt JA, Tsan R, et al. c-Met tyrosine kinase receptor expression and function in human and canine osteosarcoma cells. Clin Exp Metastasis. 2003;20(5):421-30.
72 - Ryu K, Choy E, Yang C, Susa M, Hornicek FJ, Mankin H, et al. Activation of signal transducer and activator of transcription 3 (Stat3) pathway in osteosarcoma cells and overexpression of phosphorylated-Stat3 correlates with poor prognosis. J Orthop Res. 2010;28(7):971-8.
73 - Rosenberger JA, Pablo NV, Crawford PC. Prevalence of and intrinsic risk factors for appendicular osteosarcoma in dogs: 179 cases (1996–2005). J Am Vet Med Assoc. 2007;231(7):1076-80.
74 - Phillips JC, Lembcke L, Chamberlin T. A novel locus for canine osteosarcoma (OSA1) maps to CFA34, the canine orthologue of human 3q26. Genomics. 2010;96(4):220-7.
75 - Scott MC, Sarver AL, Gavin KJ, Thayanithy V, Getzy DM, Newman RA, et al. Molecular subtypes of osteosarcoma identified by reducing tumor heterogeneity through an interspecies comparative approach. Bone. 2011;49(3):356-67.
76 - Angstadt AY, Thayanithy V, Subramanian S, Modiano JF, Breen M. A genome-wide approach to comparative oncology: high-resolution oligonucleotide aCGH of canine and human osteosarcoma pinpoints shared microaberrations. Cancer Genet. 2012;205(11):572-87.
77 - Loukopoulos P, Thornton JR, Robinson WF. Clinical and pathologic relevance of p53 index in canine osseous tumors. Vet Pathol. 2003;40(3):237-48.
78 - Wunder JS, Gokgoz N, Parkes R, Bull SB, Eskandarian S, Davis AM, et al. TP53 mutations and outcome in osteosarcoma: a prospective, multicenter study. J Clin Oncol. 2005;23(7):1483-90.
79 - Ottaviani G, Jaffe N. The epidemiology of osteosarcoma. Cancer Treat Res. 2009;152:3-13.
80 - Mendoza S, Konishi T, Dernell WS, Withrow SJ, Miller CW. Status of the p53, Rb and MDM2 genes in canine osteosarcoma. Anticancer Res. 1998;18(6A):4449-53.
81 - Freeman SS, Allen SW, Ganti R, Wu J, Ma J, Su X, et al. Copy number gains in EGFR and copy number losses in PTEN are common events in osteosarcoma tumors. Cancer. 2008;113(6):1453-61.
82 - LaRue SM, Withrow SJ, Powers BE, Wrigley RH, Gillette EL, Schwarz PD, et al. Limb-sparing treatment for osteosarcoma in dogs. J Am Vet Med Assoc. 1989;195(12):1734-44.
83 - Withrow SJ, Thrall DE, Straw RC, Powers BE, Wrigley RH, Larue SM, et al. Intra-arterial cisplatin with or without radiation in limb-sparing for canine osteosarcoma. Cancer. 1993;71(8):2484-90.
84 - Kuntz CA, Asselin TL, Dernell WS, Powers BE, Straw RC, Withrow SJ. Limb salvage surgery for osteosarcoma of the proximal humerus: outcome in 17 dogs. Vet Surg. 1998;27(5):417-22.
85 - Rougraff BT, Simon MA, Kneisl JS, Greenberg DB, Mankin HJ. Limb salvage compared with amputation for osteosarcoma of the distal end of the femur. A long-term oncological, functional, and quality-of-life study. J Bone Joint Surg Am. 1994;76(5):649-56.
86 - Thompson JP, Fugent MJ. Evaluation of survival times after limb amputation, with and without subsequent administration of cisplatin, for treatment of appendicular osteosarcoma in dogs: 30 cases (1979–1990). J Am Vet Med Assoc. 1992;200(4):531-3.
87 - Eilber F, Giuliano A, Eckardt J, Patterson K, Moseley S, Goodnight J. Adjuvant chemotherapy for osteosarcoma: a randomized prospective trial. J Clin Oncol. 1987;5(1):21-6.
88 - Link MP, Goorin AM, Miser AW, Green AA, Pratt CB, Belasco JB, et al. The effect of adjuvant chemotherapy on relapse-free survival in patients with osteosarcoma of the extremity. N Engl J Med. 1986;314(25):1600-6.
89 - Link MP, Goorin AM, Horowitz M, Meyer WH, Belasco J, Baker A, et al. Adjuvant chemotherapy of high-grade osteosarcoma of the extremity. Updated results of the Multi-Institutional Osteosarcoma Study. Clin Orthop Relat Res. 1991(270):8-14.
90 - Paoloni MC, Mazcko C, Fox E, Fan T, Lana S, Kisseberth W, et al. Rapamycin pharmacokinetic and pharmacodynamic relationships in osteosarcoma: a comparative oncology study in dogs. PLoS One. 2010;5(6):e11013.
91 - Chawla SP, Staddon AP, Baker LH, Schuetze SM, Tolcher AW, D'Amato GZ, et al. Phase II study of the mammalian target of rapamycin inhibitor ridaforolimus in patients with advanced bone and soft tissue sarcomas. J Clin Oncol. 2012;30(1):78-84.
92 - Demetri GD, Chawla SP, Ray-Coquard I, Le Cesne A, Staddon AP, Milhem MM, et al. Results of an international randomized phase III trial of the mammalian target of rapamycin inhibitor ridaforolimus versus placebo to control metastatic sarcomas in patients after benefit from prior chemotherapy. J Clin Oncol. 2013;31(19):2485-92.
93 - Gordon I, Paoloni M, Mazcko C, Khanna C. The Comparative Oncology Trials Consortium: using spontaneously occurring cancers in dogs to inform the cancer drug development pathway. PLoS Med. 2009;6(10):e1000161.
94 - Gordon IK, Khanna C. Modeling opportunities in comparative oncology for drug development. ILAR J. 2010;51(3):214-20.
95 - Lascelles BD, Dernell WS, Correa MT, Lafferty M, Devitt CM, Kuntz CA, et al. Improved survival associated with postoperative wound infection in dogs treated with limb-salvage surgery for osteosarcoma. Ann Surg Oncol. 2005;12(12):1073-83.
96 - Jeys LM, Grimer RJ, Carter SR, Tillman RM, Abudu A. Post operative infection and increased survival in osteosarcoma patients: are they associated? Ann Surg Oncol. 2007;14(10):2887-95.
97 - Wycislo KL, Fan TM. The immunotherapy of canine osteosarcoma: a historical and systematic review. J Vet Intern Med. 2015;29(3):759-69.
98 - Biller BJ, Elmslie RE, Burnett RC, Avery AC, Dow SW. Use of FoxP3 expression to identify regulatory T cells in healthy dogs and dogs with cancer. Vet Immunol Immunopathol. 2007;116(1-2):69-78.
99 - Rissetto KC, Rindt H, Selting KA, Villamil JA, Henry CJ, Reinero CR. Cloning and expression of canine CD25 for validation of an anti-human CD25 antibody to compare T regulatory lymphocytes in healthy dogs and dogs with osteosarcoma. Vet Immunol Immunopathol. 2010;135(1-2):137-45.
100 - Biller BJ, Guth A, Burton JH, Dow SW. Decreased ratio of CD8+ T cells to regulatory T cells associated with decreased survival in dogs with osteosarcoma. J Vet Intern Med. 2010;24(5):1118-23.
101 - Sherger M, Kisseberth W, London C, Olivo-Marston S, Papenfuss TL. Identification of myeloid derived suppressor cells in the peripheral blood of tumor bearing dogs. BMC Vet Res. 2012;8:209.
102 - Goulart MR, Pluhar GE, Ohlfest JR. Identification of myeloid derived suppressor cells in dogs with naturally occurring cancer. PLoS One. 2012;7(3):e33274.
103 - Selmic LE, Lafferty MH, Kamstock DA, Garner A, Ehrhart NP, Worley DR, et al. Outcome and prognostic factors for osteosarcoma of the maxilla, mandible, or calvarium in dogs: 183 cases (1986–2012). J Am Vet Med Assoc. 2014;245(8):930-8.
104 - Sottnik JL, Rao S, Lafferty MH, Thamm DH, Morley PS, Withrow SJ, et al. Association of blood monocyte and lymphocyte count and disease-free interval in dogs with osteosarcoma. J Vet Intern Med. 2010;24(6):1439-44.
105 - Kleinerman ES, Maeda M, Jaffe N. Liposome-encapsulated muramyl tripeptide: a new biologic response modifier for the treatment of osteosarcoma. Cancer Treat Res 1993;62:101-7.
106 - Kurzman ID, MacEwen EG, Rosenthal RC, Fox LE, Keller ET, Helfand SC, et al. Adjuvant therapy for osteosarcoma in dogs: results of randomized clinical trials using combined liposome-encapsulated muramyl tripeptide and cisplatin. Clin Cancer Res. 1995;1(12):1595-601.
107 - Meyers PA, Schwartz CL, Krailo MD, Healey JH, Bernstein ML, Betcher D, et al. Osteosarcoma: the addition of muramyl tripeptide to chemotherapy improves overall survival--a report from the Children's Oncology Group. J Clin Oncol. 2008;26(4):633-8.
108 - Daw NC, Neel MD, Rao BN, Billups CA, Wu J, Jenkins JJ, et al. Frontline treatment of localized osteosarcoma without methotrexate: results of the St. Jude Children's Research Hospital OS99 trial. Cancer. 2011;117(12):2770-8.
109 - Paoloni M, Khanna C. Translation of new cancer treatments from pet dogs to humans. Nat Rev Cancer. 2008;8(2):147-56.
110 - Rodriguez CO, Jr., Crabbs TA, Wilson DW, Cannan VA, Skorupski KA, Gordon N, et al. Aerosol gemcitabine: preclinical safety and in vivo antitumor activity in osteosarcoma-bearing dogs. J Aerosol Med Pulm Drug Deliv. 2010;23(4):197-206.
111 - Zhang J, Chen X, Kent MS, Rodriguez CO, Chen X. Establishment of a dog model for the p53 family pathway and identification of a novel isoform of p21 cyclin-dependent kinase inhibitor. Mol Cancer Res. 2009;7(1):67-78.
112 - Hardcastle IR, Liu J, Valeur E, Watson A, Ahmed SU, Blackburn TJ, et al. Isoindolinone inhibitors of the murine double minute 2 (MDM2)-p53 protein-protein interaction: structure-activity studies leading to improved potency. J Med Chem. 2011;54(5):1233-43.
113 - Rankin KS, Starkey M, Lunec J, Gerrand CH, Murphy S, Biswas S. Of dogs and men: comparative biology as a tool for the discovery of novel biomarkers and drug development targets in osteosarcoma. Pediatr Blood Cancer. 2012;58(3):327-33.
114 - Fieten H, Spee B, Ijzer J, Kik MJ, Penning LC, Kirpensteijn J. Expression of hepatocyte growth factor and the proto-oncogenic receptor c-Met in canine osteosarcoma. Vet Pathol. 2009;46(5):869-77.
115 - Atkinson JM, Falconer RA, Edwards DR, Pennington CJ, Siller CS, Shnyder SD, et al. Development of a novel tumor-targeted vascular disrupting agent activated by membrane-type matrix metalloproteinases. Cancer Res. 2010;70(17):6902-12.
116 - Eisenach PA, Roghi C, Fogarasi M, Murphy G, English WR. MT1-MMP regulates VEGF-A expression through a complex with VEGFR-2 and Src. J Cell Sci. 2010;123(23):4182-93.