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Multicenter Study
. 2018 Mar;7(3):677-689.
doi: 10.1002/cam4.1350. Epub 2018 Feb 14.

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

Hiromitsu Iwata  1   2 , Hitoshi Ishikawa  3 , Masaru Takagi  4   5 , Tomoaki Okimoto  5 , Sigeyuki Murayama  6 , Tetsuo Akimoto  7 , Hitoshi Wada  8 , Takeshi Arimura  9 , Yoshitaka Sato  10 , Masayuki Araya  11 , Jun-Etsu Mizoe  1 , Masahiko Gosho  12 , Katsumasa Nakamura  13 , Hiroki Shirato  14 , Hideyuki Sakurai  3
Affiliations
Multicenter Study

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

Hiromitsu Iwata et al. Cancer Med. 2018 Mar.

Abstract

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.

Keywords: Biochemical relapse-free survival; late toxicity; multi-institutional survey; prostate cancer; proton therapy.

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Figures

Figure 1
Figure 1
Biochemical relapse‐free survival according to the NCCN classification. Significant differences were observed in treatment results among the three groups (red line, low risk; pink line, intermediate risk; blue line, high risk).
Figure 2
Figure 2
Overall survival (A), cause‐specific survival (B), biochemical relapse‐free (C), and clinical relapse‐free curves (D) according to the NCCC group (red line, low risk; pink line, intermediate risk; blue line, high risk).
Figure 3
Figure 3
Cumulative incidence rates of the late grade 2 or more severe gastrointestinal toxicity curve (A) and late genitourinary toxicity curve (B).
See this image and copyright information in PMC

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