Salvage High-Dose Rate (HDR) Brachytherapy as a Treatment for Locally Recurrent Prostate Cancer after Primary Radiation Therapy

Abstract

Salvage brachytherapy is a treatment option for patients with locally recurrent prostate cancer following definitive radiotherapy. We report the tumor control and toxicity outcomes from using high-dose rate (HDR) brachytherapy (BT) alone for local salvage. Between 2013 and 2017, thirty-two patients with biopsy-proven (n = 23) or radiologically-evident (n = 9) locally recurrent prostate cancer were treated with salvage HDR brachytherapy. Dose-fractionation schedules included: 19Gy single fraction (n = 24), 15Gy single fraction (n = 5), 26Gy in two fractions (n = 2) and 31.5Gy in three fractions (n = 1). Three patients received treatment to the whole gland; the remaining 29 received focal therapy mapped according to combined pelvic magnetic resonance (MR) imaging and template biopsy findings (n = 21) or MR imaging alone (n = 8). The median time from completion of primary treatment to salvage HDR BT was 57 months. Seventeen patients received androgen deprivation therapy (ADT) as part of their primary treatment. In all cases, ADT had been discontinued prior to salvage HDR BT and was not re-commenced following the procedure. Biochemical progression-free survival (bPFS) using the Kaplan-Meier method was defined according to the Phoenix standard of nadir prostate-specific antigen (PSA) plus ≥2mg/ml. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicities were evaluated using the Common Terminology Criteria for Adverse Events, version 4.0. Late toxicity was defined as that occurring ≥90 days after completion of salvage brachytherapy. Median follow-up after salvage HDR brachytherapy was 24 months. Median PSA nadir value was 0.8 reached at a median of 5 months from day of implant. The 2-year biochemical progression-free survival rate was 60.0%. The 2-year local relapse rate was 9.3% with 8 out of the 11 recurrences occurring at distant sites. Acute and late GU and GI toxicities are shown in Table 1. Two patients developed late grade 3 urinary toxicity, both urethral strictures requiring surgical correction. No late GI complications of grade 2 or higher were encountered with no reports of rectal fistulae or requirement for defunctioning colostomy.Abstract SU_28_2277; Table 1Number of patients presenting with acute (<90 days) and late (≥90 days) genitourinary and gastrointestinal toxicities following salvage high-dose rate brachytherapyToxicityACUTELATEGenitourinarynnGrade 1/22219Grade 302Grade 400GastrointestinalGrade 1/241Grade 300Grade 400 Open table in a new tab High-dose rate brachytherapy is an effective modality for the salvage treatment of locally recurrent prostate cancer with very good local control rates and an acceptable long-term toxicity profile. The high rate of distant relapse underscores the current challenge of accurate staging of systemic disease and appropriate patient selection in the salvage setting. The use of more sensitive imaging modalities such as PSMA-PET may improve this in the future.