Salvage high dose rate brachytherapy for recurrent prostate cancer after definitive radiation.

Abstract

PURPOSE\nSalvage high-dose-rate brachytherapy (sHDRBT) for locally recurrent prostate cancer after definitive radiation is associated with biochemical control in approximately half of patients at 3-5 years. Given potential toxicity, patient selection is critical. We present our institutional experience with sHDRBT and validate a recursive partitioning machines model for biochemical control.\n\n\nMATERIALS AND METHODS\nWe performed a retrospective analysis of 129 patients who underwent whole-gland sHDRBT between 1998-2016. We evaluated clinical factors associated with biochemical control as well as toxicity.\n\n\nRESULTS\nAt diagnosis the median PSA was 7.77 ng/mL. Majority of patients had T1-2 (73%) and Gleason 6-7 (82%) disease. 71% received external beam RT alone, while 22% received permanent prostate implants. The median disease free interval (DFI) was 56 months, and median pre-salvage PSA was 4.95ng/mL. At sHDRBT, 46% had T3 disease and 51% had Gleason 8-10 disease. At a median of 68 months following sHDRBT, 3 and 5-year disease free survival were 85% (95% CI 79-91%) and 71% (95% CI 62-79%), respectively. Median PSA nadir was 0.18 ng/mL, achieved a median of 10 months after sHDRBT. Patients with ≥35%+ cores and a DFI <4.1 years had worse biochemical control (19% vs. 50%, p\u202f=\u202f0.02). Local failure (with or without regional/distant failure) was seen in 11% of patients (14/129). 14 patients (11%) developed acute urinary obstruction requiring Foley placement and 19 patients (15%) developed strictures requiring dilation.\n\n\nCONCLUSIONS\nsHDRBT is a reasonable option for patients with locally recurrent prostate cancer following definitive RT. Those with <35%+ cores or an initial DFI of ≥4.1 years may be more likely to achieve long-term disease control following sHDRBT.