Long-term outcomes of moderately hypofractionated radiotherapy (67.5 Gy in 25 fractions) for prostate cancer confined to the pelvis: a single center retrospective analysis

Background There is an increasing application of moderately hypofractionated radiotherapy for prostate cancer. We presented our outcomes and treatment-related toxicities with moderately hypofractionated (67.5 Gy in 25 fractions) radiotherapy for a group of advanced prostate cancer patients from China. Methods From November 2006 to December 2018, 246 consecutive patients with prostate cancer confined to the pelvis were treated with moderately hypofractionated radiotherapy (67.5 Gy in 25 fractions). 97.6% of the patients received a different duration of androgen deprivation therapy. Failure-free survival (FFS), prostate cancer-specific survival (PCSS), overall survival (OS), and cumulative grade >= 2 late toxicity were evaluated using the Kaplan-Meier actuarial method. Prognostic factors for FFS, PCSS, and OS were analyzed. Results The median follow-up time was 74 months (range: 6-150 months). For all patients, the 5- and 10-year FFS rates were 80.0% (95% CI: 74.7-85.7%) and 63.5% (95% CI 55.4-72.8%). The failure rates for the intermediate, high-risk, locally advanced, and N1 groups were 6.1%, 13.0%, 18.4%, and 35.7%, respectively (P = 0.003). Overall, 5- and 10-year PCSS rates were 95.7% (95% CI 93.0-98.5%) and 88.2% (95% CI 82.8-93.8%). Prostate cancer-specific mortality rates for the high-risk, locally advanced, and N1 groups were 4.0%, 8.2%, and 23.8%, respectively (P < 0.001). Overall, 5- and 10-year actuarial OS rates were 92.4% (95% CI 88.8-96.1%) and 72.7% (95% CI 64.8-81.5%). High level prostate-specific antigen and positive N stage were significantly associated with worse FFS (P < 0.05). Advanced T stage and positive N stage emerged as worse predictors of PCSS (P < 0.05). Advanced age, T stage, and positive N stage were the only factors that were significantly associated with worse OS (P < 0.05). The 5-year cumulative incidence rate of grade >= 2 late GU and GI toxicity was 17.8% (95% CI 12.5-22.7%) and 23.4% (95% CI 17.7-28.7%), respectively. Conclusions Moderately hypofractionated radiotherapy (67.5 Gy in 25 fractions) for this predominantly high-risk, locally advanced, or N1 in Chinese patients demonstrates encouraging long-term outcomes and acceptable toxicity. This fractionation schedule deserves further evaluation in similar populations.