Magnetic Resonance Image Guided Salvage Brachytherapy Following Radiation in Select Men who Initially Presented With Favorable-risk Prostate Cancer: A Prospective Phase II Study

Abstract

To prospectively evaluate the late gastrointestinal (GI) and genitourinary (GU) toxicity and prostate-specific antigen (PSA) control of magnetic-resonance imaging (MRI)-guided brachytherapy used as salvage for radiation therapy (RT) failure. From 10/00 to 10/05, 25 men with a rising PSA and biopsy-proven intraprostatic cancer at least 2 years after initial RT (13 external beam, 12 brachytherapy) who had favorable clinical features (Gleason score ≤7, PSA <10, negative pelvic and bone imaging), received MRI-guided salvage brachytherapy to a minimum peripheral dose of 137 Gray on a Phase I/II protocol. The Kaplan-Meier method was used to estimate the rates of treatment toxicity and cancer control. Median follow-up was 47 months. The 4-year estimate of grade 3 or 4 GI/GU toxicity was 30%. Thirteen percent of patients required a colostomy and/or urostomy to repair a fistula. An interval <4.5 years between radiation courses was associated with both outcomes with hazard ratio of 12.0 (95% CI = 1.4 to 100; p = 0.02) for grade 3 or 4 toxicity and 25.0 (95% CI = 1.1 to 529; p = 0.04) for colostomy and/or urostomy. The PSA control, using the Phoenix definition, was 70% at 4-years. MRI-guided salvage brachytherapy in select men based on presenting characteristics and post-failure PSA kinetics can achieve high PSA control rates, but complications requiring surgical intervention may occur in 10 to 15% of men. Prospective randomized studies are needed to characterize the relative cancer control and toxicity following all forms of salvage local therapy.