Login to Access Video or Poster Abstract: MP05-07
Sources of Funding: none

Introduction

We sought to identify variables that may predict persistent hypogonadism and castration in patients with prostate cancer (PCa) treated with brachytherapy (BT).

Methods

A retrospective analysis was performed on a prospectively maintained database of patients receiving BT ± external beam radiation therapy (EBRT) ± hormone therapy (HT) for NCCN low, intermediate or high-risk prostate cancer at a single institution between 1990-2011 with a minimum follow-up of 5 years. Patients were categorized as receiving no HT (n=438, 41.6%), ≤ 6 months (n=317, 31.1%) or > 6 months (n=298, 28.3%) of HT. Those receiving combination HT within one year of final testosterone (T) measurement were excluded, as well as patients receiving salvage ADT at any time. 5 and 10-year freedom from persistent hypogonadism (T<280 ng/dL) and castration (T<50 ng/dL) for each group was evaluated with Kaplan-Meier estimates. Multivariable cox proportional hazards models were used to compare risk of persistent hypogonadism and castration at a median follow-up of 6.5 years (post-treatment to final T) (IQR: 4.3-9.1 years; Range: 1.0-19.2 years).

Results

Of 1,981 patients receiving BT for clinically localized PCa, 1,053 met inclusion criteria. The 5-year freedom from hypogonadism rates were 92.4%, 88.9% and 87.0% for patients with no HT, ≤ 6 months and > 6 months of HT, respectively (10-year rates: 66.7%, 55.3%, 40.5%); 5-year freedom from castration rates were 99.2%, 98.0% and 98.4%, respectively (10-year rates: 97.9%, 95.5%, 90.9%). In multivariable analyses, number of months of HT (continuous variable, HR=1.04, p=.030) and BT with EBRT vs. BT alone (HR=1.56, p=.010) significantly increased the risk of persistent hypogonadism. Older age (HR=1.04, p<.001) and diabetes (HR=1.43, p=.048) were also significant. Number of months of HT was the only variable which increased the risk of persistent castration (HR=1.09, p=.014).

Conclusions

EBRT is an independent risk factor for persistent hypogonadism among patients receiving BT for PCa. The mechanism of this finding needs to be elucidated, but may be secondary to scatter radiation during EBRT. Prolonged HT additionally increases the risk for persistent hypogonadism and castration.

Funding

none