Ryohei Sasaki

By Ryohei Sasaki, Hiroaki Akasaka, Yusuke Demizu, Sachiko Inubushi, Tianyuan Wang and Takumi Fukumoto

The authors aimed to introduce a medical application for nonwoven fabric as spacers in particle therapy. Particle therapy, exhibiting more focused effects on target tissues, has emerged as a promising treatment modality. However, close proximity of tumor tissue and adjacent organs makes delivery of curative doses to the tumor difficult because severe radiation morbidities might occur. A method using surgically placed GORE-TEX sheets as a spacer has been reported. Although this method provides for separation of adjacent organs, the material is not resorbed. To overcome these anatomical and therapeutic difficulties, and to deliver effective radiation doses to treat upper abdominal tumors, we have developed a nonwoven fabric spacer composed of bioabsorbable suture material. The absorbable polyglycolic acid (PGA) spacer had water-equivalent, biocompatible, and thickness-retaining properties. Although further evaluation is warranted in a clinical setting, the PGA spacer may be effective to block particle beams and to separate normal tissues from the radiation field. These findings suggest that the nonwoven-fabric PGA spacer might become a useful device in particle therapy.

Part of the book: Non-woven Fabrics

By Hiroaki Akasaka, Naritoshi Mukumoto, Masao Nakayama, Tianyuan Wang, Ryuichi Yada, Yasuyuki Shimizu, Saki Osuga, Yuki Wakahara and Ryohei Sasaki

This chapter discusses the clinical application and implementation of wedge techniques in radiation therapy. Coverage of the target region with a curative dose is critical for treating several cancer types; to that end, wedge filters are commonly used to improve dose uniformity to the target volume. Initially, wedges designed for this purpose were physical and were made of high-density materials such as lead or steel. Subsequently, nonphysical wedges were introduced; these improved the dose uniformity using computer systems in lieu of physical materials. As wedge systems evolve, however, they each continue to have their advantages and disadvantages. When using physical wedges, it is difficult to control the generation of secondary radiation resulting from the collision of the radiation beam with the wedge body; conversely, nonphysical wedges do not create any secondary radiation because there is no physical interference with the beam. On the other hand, nonphysical wedges are less suitable for treating moving tumors, such as those in the lung, and physical wedges have better dose coverage to the target volume than nonphysical wedges. This chapter aims to guide decision-making regarding the choice of wedge types in various clinical situations.

Part of the book: Radiotherapy

By Yasuo Ejima, Takeaki Ishihara, Daisuke Miyawaki, Kenichiro Kakutani, Kotaro Nishida, Junichiro Inoue, Yoshitada Sakai, Tianyuan Wang and Ryohei Sasaki

Proper care of patients with bone metastasis requires interdisciplinary treatments. Radiotherapy (RT) plays a central role in the management of painful bone metastasis. External beam RT can provide rapid successful palliation of painful bone metastasis in 50–80% of patients, is associated with very few adverse effects and leads to complete pain relief at the treated site in up to one‐third of patients. Intensity‐modulated RT (IMRT) or stereotactic body RT (SBRT) enables the delivery of higher doses to the target tumor while minimizing the dose to adjacent organs. Reirradiation using IMRT or SBRT is a valuable option for the management of bone metastases. A multidisciplinary team, especially one consisting of a spinal surgeon and rehabilitation physician, is particularly useful for treating patients with spinal bone metastases characterized by spinal instability. Rehabilitation intervention which increases the physical activity level and prevents deconditioning is important. Future developments in surgical procedures and RT will likely improve the management protocols for bone metastases and technology to reduce metal artifacts in radiation planning might improve the efficacy and safety of combination therapy.

Part of the book: Radiotherapy

By Ai Nakaoka, Kana Kobayashi, Mennaallah Hassan and Ryohei Sasaki

Exosomes are a subgroup of extracellular vesicles that are released by all types of cells, including tumor cells, and mediate intercellular communication via the transport of various intracellular components, including microRNAs, messenger RNAs, and proteins. Radiation produces reactive oxygen species and induces DNA double-strand break in cancer cells and normal cells. Cancer cells have severe damage and die by irradiation, but normal cells can keep proliferation with their high DNA repair ability. Irradiated cells generate communication signals and cause biological changes in neighboring or distant non-irradiated cells. This review outlines the role of exosomes in radiation therapy. In the tumor microenvironment, exosomes are considered to regulate cell survival, migration, and resistance to therapy by interacting with vascular endothelial cells and various types of immune cells. Nowadays, radiation therapy is typically combined with immunotherapy. Regulation of the activity of exosomes may overcome the problem of resistance to immunotherapy. Furthermore, exosomes can attenuate resistance to chemotherapy by transporting certain types of microRNA. The current evidence suggests that exosomes may be useful in the diagnosis and treatment of cancer in the future.

Part of the book: Extracellular Vesicles