Long-term outcomes of proton therapy for prostate cancer in Japan: a multi-institutional survey of the Japanese Radiation Oncology Study Group

This is the first multi-institutional retrospective survey of the long-term outcomes of proton therapy (PT) for prostate cancer in Japan. This retrospective analysis comprised prostate cancer patients treated with PT at seven centers between January 2008 and December 2011 and was approved by each Institutional Review Board. The NCCN classification was used. Biochemical relapse was based on the Phoenix definition (nadir + 2.0 ng/mL). Toxicities were evaluated with the Common Terminology Criteria for Adverse Events version 4.0. There were 215, 520, and 556 patients in the low-risk, intermediate-risk, and high-risk groups, respectively. The median follow-up period of surviving patients was 69 months (range: 7-107). Among all patients, 98.8% were treated using a conventional fractionation schedule and 1.2% with a hypofractionation schedule; 58.5% and 21.5% received neoadjuvant and adjuvant androgen deprivation therapy, respectively. The 5-year biochemical relapse-free survival (bRFS) and overall survival rates in the low-risk, intermediate-risk, and high-risk groups were 97.0%, 91.1%, and 83.1%, and 98.4%, 96.8%, and 95.2%, respectively. In the multivariate analysis, the NCCN classification was a significant prognostic factor for bRFS, but not overall survival. The incidence rates of grade 2 or more severe late gastrointestinal and genitourinary toxicities were 4.1% and 4.0%, retrospectively. This retrospective analysis of a multi-institutional survey suggested that PT is effective and well-tolerated for prostate cancer. Based on this result, a multi-institutional prospective clinical trial (UMIN000025453) on PT for prostate cancer has just been initiated in order to define its role in Japan.

Cancer medicine. 2018 Feb 14 [Epub ahead of print]

Hiromitsu Iwata, Hitoshi Ishikawa, Masaru Takagi, Tomoaki Okimoto, Sigeyuki Murayama, Tetsuo Akimoto, Hitoshi Wada, Takeshi Arimura, Yoshitaka Sato, Masayuki Araya, Jun-Etsu Mizoe, Masahiko Gosho, Katsumasa Nakamura, Hiroki Shirato, Hideyuki Sakurai

Department of Radiation Oncology, Nagoya Proton Therapy Center, Nagoya City West Medical Center, Nagoya, Japan., Department of Radiation Oncology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan., Department of Radiation Oncology, Sapporo Teishinkai Hospital, Sapporo, Japan., Department of Radiology, Hyogo Ion Beam Medical Center, Tatsuno, Japan., Proton Therapy Division, Shizuoka Cancer Center Hospital, Nagaizumi, Japan., Division of Radiation Oncology and Particle Therapy, National Cancer Center Hospital East, Kashiwa, Japan., Department of Radiation Oncology, Southern TOHOKU Proton Therapy Center, Koriyama, Japan., Medipolis Proton Therapy and Research Center, Ibusuki, Japan., Proton Therapy Center, Fukui Prefectural Hospital, Fukui, Japan., Proton Therapy Center, Aizawa Hospital, Matsumoto, Japan., Department of Clinical Trial and Clinical Epidemiology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan., Department of Radiation Oncology, Hamamatsu University School of Medicine, Hamamatsu, Japan., Department of Radiation Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan.