Large prostate gland size is not a contraindication to low-dose-rate brachytherapy for prostate adenocarcinoma

Abstract

Prostate volume greater than 50cc is traditionally a relative contraindication to prostate seed implantation (PSI), but there is little consensus regarding prostate size and clinical outcomes. We report biochemical control and toxicity after low-dose-rate PSI and compare outcomes according to the prostate size. A total of 429 men who underwent low-dose-rate PSI between 1998 and 2009 were evaluated. Median followup was 38.7 months. Patients were classified by prostate volume into small, medium, and large subgroups. Differences were analyzed using the Mann-Whitney and Pearson's χ(2) tests for continuous and categorical variables, respectively. Cox proportional hazards regression models were used to evaluate effect of prostate size on outcomes. Patient pretreatment factors were balanced between groups except for age (p=0.001). The 10-year actuarial freedom from biochemical failure for all patients treated with PSI was 96.3% with no statistically significant difference between large vs. small/medium prostate size (90% vs. 96.6%, p=0.47). In a multivariate analysis, plan type (hazard ratio [HR]=0.25, p=0.03), dose to 90% of the gland (D90: HR=0.98, p=0.02), volume receiving 200Gy (V200: HR=0.98, p=0.026), and biologic effective dose (HR=0.99, p=0.045), but not prostate size (HR=2.27, p=0.17) were significantly associated with freedom from biochemical failure. Prostate size was not significantly associated with time to maximum American Urologic Association score. In men with large prostates, the PSI provides biochemical control and temporal changes in genitourinary toxicity that are comparable with men having smaller glands. Accurate dose optimization and delivery of PSI provides the best clinical outcomes regardless of gland size.