5-Year Outcomes of a Prospective Phase 1/2 Study of Accelerated Hypofractionated Radiation Therapy to the Prostate Bed.

Abstract

PURPOSE\nTo report the 5-year outcomes from a single institution, prospective, phase 1/2 study on hypofractionated, accelerated radiation therapy to the prostate bed after radical prostatectomy.\n\n\nMETHODS AND MATERIALS\nPatients enrolled in this study were all eligible for postoperative radiation therapy and received a prescribed dose of 51\xa0Gy in 17 fractions to the prostate bed. On follow-up, gastrointestinal (GI) and genitourinary (GU) toxicity was assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0; prostate-specific antigen (PSA) was evaluated and quality of life was assessed using the Expanded Prostate Cancer Index Composite (EPIC) questionnaire.\n\n\nRESULTS\nA total of 30 patients were enrolled between 2008 and 2011. Median age was 65 (52-75) years. Median pretreatment PSA was 0.12\xa0ng/mL (0.01-1.42). Twenty-six (93%) patients had Gleason ≤7 disease, 13 (43%) had pT3 disease, and 20 (67%) had positive margins. Twenty-six patients (87%) underwent radiation therapy as salvage treatment. After a median follow-up of 6.4 (2.1-8.1) years, no patient experienced Common Terminology Criteria for Adverse Events grade 3/4 toxicity. Eleven patients (37%) had grade 2 genitourinary and 2 (7%) had grade 2 gastrointestinal toxicity. At baseline and 5\xa0years after radiation therapy, mean EPIC urinary domain score was 80% (standard deviation, 18%) and 82% (17%). Mean EPIC bowel domain score was 93% (13%) and 93% (15%). One patient (4%) had a minimally clinically important change in urinary domain score and 1 patient (4%) had a minimally clinically important change in bowel domain score. Nelson-Aalen estimated cumulative incidence of biochemical failure was 31% (nadir +0.2) and 18% (nadir +2.0) at 5\xa0years. Four-year PSA ≥0.4 was predictive of subsequent androgen deprivation therapy use (Nelson-Aalen cumulative incidence: 1.45; P\xa0<\xa0.0001). Five patients (17%) received hormonal therapy for biochemical failure. Nelson-Aalen estimated cumulative incidence of hormone therapy use was 14% at 5\xa0years. All patients who received hormone therapy had PSA >0.4 at 4\xa0years.\n\n\nCONCLUSIONS\nIn this phase 1/2 study, hypofractionated postoperative radiation therapy seems to have good clinical efficacy without significant late toxicity. Phase 3 studies are warranted.