Dose-intensified Versus Conventional-dose Salvage Radiotherapy for Biochemically Recurrent Prostate Cancer After Prostatectomy: Long-term Data from the SAKK 09/10 Randomised Phase 3 Trial

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.