A cohort of 146 patients with low-risk prostate cancer were treated to 60 Gy (cobalt Gy equivalent) of proton therapy (20 fractions of 3.0 Gy per fraction) in 4 weeks. With the median followup of 42 months, this study reported that acute grade 2 urinary toxicity occurred in 16% of the patients; acute grade 2 or higher gastrointestinal toxicity was seen in 1.7%.

At 9 months, 1 patient had late grade 3 urinary toxicity, which resolved by 12 months; no grade 3 gastrointestinal toxicities occurred. The 3-year biochemical survival rate was 99.3% (144/145). This study made a conclusion that hypofractionated proton therapy of 60 Gy in 20 fractions was safe and effective for patients with low-risk prostate cancer.