We report long-term outcomes from the phase 3 SAKK 09/10 trial that randomly assigned men with biochemical progression after radical prostatectomy to conventional-dose (64 Gy) or dose-intensified (70 Gy) salvage radiotherapy (SRT) to the prostate bed without hormonal therapy. The primary endpoint was freedom from biochemical progression (FFBP). Secondary endpoints included clinical progression-free survival (PFS), time to hormonal treatment, overall survival (OS), and late toxicity. Between February 2011 and April 2014, 350 patients were randomly assigned (175 per arm). Median prostate-specific antigen (PSA) at randomization was 0.3 ng/ml. After median follow-up of 8.6 yr, median FFBP was 8.7 yr (95% confidence interval CI 7.1-not reached NR) after 64 Gy and 8.7 yr (95% CI 6.7-NR) after 70 Gy (log-rank p = 0.87), with a hazard ratio of 1.03 (95% CI 0.75-1.41). There was no significant difference in clinical PFS, time to hormonal treatment, or OS. While late genitourinary toxicity did not significantly differ between the arms, late grade 2 and 3 gastrointestinal toxicity was more frequent with 70 Gy (p = 0.015). After long-term follow-up dose-intensified SRT was not superior to conventional-dose SRT, but was associated with a higher rate of late grade ≥2 gastrointestinal toxicity. PATIENT SUMMARY: The optimal radiotherapy dose for patients who have higher levels of tumor markers after surgery for prostate cancer is unclear. Our long-term follow-up confirms that a higher dose only increases the chances of gastrointestinal side effects without providing any benefits to the patient. This trial is registered on ClinicalTrials.gov as NCT01272050.
Ghadjar et al. (Sun,) studied this question.