Every Other Day or Once a Week: Long-term Oncological Outcomes in the Phase 2 PATRIOT Trial of Prostate Stereotactic Ablative Body Radiotherapy.

Background and objective: The PATRIOT multicentre phase 2 trial showed that prolongation of overall treatment time (OTT) for prostate stereotactic ablative body radiotherapy (SABR) was associated with better acute bowel and urinary quality of life. However, the impact on long-term cancer outcomes is unclear.

Methods: Men with favourable-risk localised prostate cancer in the PATRIOT trial were randomised to five-fraction prostate SABR every other day (EOD; n = 77) or once weekly (QW; n = 75).The cancer outcomes evaluated in this post hoc analyses were biochemical failure (BF), metastasis-free survival (MFS), prostate cancer-specific survival (PCSS), and overall survival (OS).

Key findings and limitations: Median follow-up was 91 mo. The 8-yr cumulative incidence rates for BF were 5.5% in the EOD arm versus 9.6% the QW arm (p = 0.2). The 8-yr probability rates were 100% versus 95.9% for MFS (p = 0.08), 100% versus 97.2% for PCSS (p = 0.2), and 96.0% versus 85.4% for OS (p = 0.3) for the EOD versus QW arms, respectively. The study is limited by the small sample size (powered to detect significant differences in acute bowel quality of life).

Conclusions: This study suggests no significant differences in long-term cancer outcomes between EOD and QW schedules for five-fraction prostate SABR. This trial is registered on ClinicalTrials.gov as NCT01423474.