Biochemical control and 2-year tolerability following stereotactic body radiotherapy for localized prostate cancer: a multicenter study in Spain.

[PURPOSE] To assess 2-year biochemical control, radiological progression, late side effects, and survival outcomes following stereotactic body radiotherapy (SBRT) for localized prostate cancer in a multicenter Spanish cohort.

[METHODS] A total of 250 patients with localized prostate cancer treated with SBRT across 12 Spanish centers between January 2020 and December 2023 were analyzed. Biochemical recurrence was defined according to the Phoenix criterion (nadir PSA + 2 ng/mL). Late genitourinary (GU), gastrointestinal (GI), and sexual adverse events were assessed using the Common Terminology Criteria for Adverse Events (CTCAE) v5.0. Univariate and multivariate analyses were performed to identify factors associated with outcomes. Survival was estimated using the Kaplan-Meier method and the log-rank test (p < 0.05).

[RESULTS] The median age was 72 years (IQR: 65-76), and the median baseline PSA was 6.7 ng/mL (5.3-8.7). According to the NCCN classification, 30% of patients were low risk, 67% intermediate (26.8% favorable, 39.6% unfavorable), and 3% high or very high risk. The median prescribed dose was 40 Gy in five fractions (36.25-40.0), administered on alternate days. At 2 years, biochemical control was 96.4%, and radiological progression occurred in 2.8% of patients, predominantly nodal. The incidence of grade ≥ 2 late adverse events was 7.6% GU, 1.2% GI, and 14.3% sexual.

[CONCLUSIONS] SBRT for localized prostate cancer offers excellent 2-year biochemical control with low rates of late adverse events, supporting its safety and effectiveness in routine clinical practice for selected patients. A longer follow-up is warranted to fully characterize long-term outcomes.