Salvage low-dose-rate permanent seed brachytherapy for locally recurrent prostate cancer: Association between dose and late toxicity.

Purpose: Rates of late toxicity are higher for salvage treatment of local recurrence after prior radiotherapy. We present our experience with salvage prostate brachytherapy (BT) for local recurrence after definitive external beam radiotherapy with attention to the relationship between dose and late toxicity.
Methods and Materials: From 2005 to 2012, 18 patients with biopsy proven locally recurrent prostate cancer and negative staging received low-dose-rate BT with a prescribed dose of 130-144 Gy. Toxicities were graded using Common Terminology Criteria for Adverse Events, version 3.0.
Results: Median followup is 31.5 months (range, 12-104). International Prostate Symptom Scores peaked at 3 months (median, 21/35), returning to baseline by 24 months. Urinary catheterization rate was 33% (median duration, 14 days; range, 1-90 days). Late Grade 3/4 genitourinary toxicity occurred in 1 patient each, one of whom also had Grade 3 late gastrointestinal toxicity; urethral strictures developed in three others. These 5 patients with late toxicity had higher dose to the prostate (isodose enclosing 90% [D90] median, 151 Gy; range, 135-185 Gy) compared with those without late complications (median, 134 Gy; range, 105-165; p < 0.04). Acute gastrointestinal toxicity Grade <3 occurred in 44%. Four patients (22%) experienced biochemical failure.
Conclusion: Salvage low-dose-rate prostate BT can provide durable biochemical control. Care should be taken to select patients with higher likelihood of organ-confined disease. The goal of planning should be to treat the recurrent disease to an adequate dose with careful attention to maintain a conservative D90.
(Copyright © 2015 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.)