Management of isolated local failures following stereotactic body radiation therapy for low to intermediate risk prostate cancer.

66Background: SBRT is a safe and effective treatment option for patients with low to intermediate risk prostate cancer (PCa). SBRT delivers high biologically effective doses resulting in very low PSA nadirs. Strategies to diagnose and confirm salvageable isolated local failures (ILF) are needed. This study aims to examine the incidence and approach to management of ILF after SBRT in a large single institution cohort. Methods: All patients with low or intermediate risk PCa treated with SBRT at our institution were eligible for this study. Treatment was delivered using the robotic SBRT with doses of 35-36.25 Gy in five fractions. ILF were diagnosed using mpMRI and/or biopsy prompted by PSA rise after achieving long-term nadir. Choice of salvage therapy and post-salvage PSA were ascertained on follow up. Results: Between December, 2008 to August, 2018, 998 men with low to intermediate risk prostate cancer were eligible for analysis. Twenty patients (low risk, n = 4; intermediate risk, n = 16) were found to h...