Five-year results from a phase I/II study of moderately hypofractionated intensity-modulated radiation therapy (IMRT) for localized prostate cancer including simultaneously integrated boost and pelvic lymph node (LN) coverage.

Abstract

299 Background: This study reports the 5 year toxicity and efficacy data of a phase I/II trial of moderately hypofractionated intensity modulated radiation therapy (IMRT) for localized prostate cancer utilizing a simultaneous integrated boost and pelvic lymph node (LN) coverage. Methods: Men with localized prostate cancer were prospectively enrolled and received IMRT to the prostate +/- seminal vesicles (SVs) +/- LNs based on National Comprehensive Cancer Network (NCCN) guidelines. Low-risk (LR) patients received 69.6 Gy in 29 fractions to the prostate alone; intermediate-risk (IR) and high-risk (HR) patients received 72Gy to the prostate, 54Gy to the SVs, and 50.4Gy to LNs (if risk of LN involvement > 15% by the Roach formula) all in 30 fractions. IR and HR patients received androgen deprivation therapy. Results: Fifty-five patients were enrolled and 49 patients evaluable with a median follow up of 60 months. There were 11 (20%) LR, 23 (41.8%) IR, and 21 (38.2%) HR patients. Twenty-five patients (51%) received prostate and LN treatment. At 5 years, the cumulative incidence of late grade 2+ gastrointestinal (GI) and genitourinary (GU) toxicity was 22.6% and 38.2% respectively. Prevalence rates of late grade 2 GI toxicity at 1, 3, and 5 years was 5.8%, 3.9%, and 5.8% respectively. Late grade 2+ GI toxicities that did not resolve by 60 months included 3 out of 52 patients (5.8%). Prevalence rates of late grade 2 GU toxicity at 1, 3, and 5 years rates were 15.4%, 7.7%, and 13.5% respectively. There were 3 patients (5.8%) who experienced grade 3 GU toxicity and no grade 3 GI toxicities. The biochemical relapse free survival at 5 years for the cohort was 88.3%. There were no local, regional, or distant failures, with all patients still alive at last follow up. Conclusions: Moderate hypofractionation of localized prostate cancer utilizing a simultaneous integrated boost and LN coverage produces excellent biochemical control and acceptable acute/late toxicity. This phase I/II trial adds to maturing data with 5 year outcomes which justify its use for cost and patient convenience factors. Clinical trial information: NCT01117935.