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.