A Phase II Study of Salvage High-Dose-Rate Brachytherapy for the Treatment of Locally Recurrent Prostate Cancer after Definitive External Beam Radiotherapy

Abstract

Patients who develop local recurrence in the prostate after definitive external beam radiotherapy have limited salvage treatment options. A phase II study of high-dose-rate (HDR) brachytherapy alone as a salvage therapy was undertaken. Toxicity and biochemical control were the endpoints of the study. Forty-two patients with biopsy proven recurrence were enrolled on an IRB-approved phase II study of salvage HDR monotherapy. Accrual was completed in 2011. 3200cGy was delivered in 4 fractions over 30 hours in a single insertion. Patients were assessed every three months. Toxicity was assessed with the International Prostate Symptom Scale (IPSS), NCI Common Terminology for Adverse Events (CTAE) v3 acute and late GU and GI domains, and International Index of Erectile Function (IIEF). Serum PSA was also evaluated at each followup visit. Biochemical relapse was defined with the nadir + 2 definition. Forty patients had a minimum followup of 3 months. Median pretreatment EBRT dose was 8100cGy (6840-8640cGy) and the median time from completion of EBRT to salvage HDR was 73 months. Median followup after salvage HDR was 38 months (6-67 months). Median pre salvage PSA was 3.45 ng/mL and the median PSA at last followup was 0.57 ng/mL. The actuarial PSA bNED at median followup and at 5 years was 70% (N=9 failures). Twelve patients had received hormonal therapy prior to salvage HDR, but HT was discontinued after treatment in all cases. The median time to biochemical failure was 9 months from the time of salvage treatment. Three patients have developed evidence of metastatic disease. Cause-specific survival was 94%. GU toxicity was the most commonly encountered complication of salvage HDR. Salvage HDR is an effective and well tolerated modality for local recurrent prostate cancer, and should be considered for even for patients who have previously been treated with ultra high dose EBRT.