Relationship of Biochemical Outcome to Percentage of Positive Biopsies in Men with Clinically Localized Prostate Cancer Treated with Permanent Interstitial Brachytherapy

Objectives Recent studies have demonstrated that the percentage of positive prostate needle biopsies (PPBs) is an independent predictor of biochemical failure (BF) after radical prostatectomy and external beam radiotherapy. Few studies have confirmed this phenomenon in patients treated with permanent interstitial brachytherapy. We conducted an analysis to determine the clinical utility of the PPBs in predicting BF after permanent interstitial brachytherapy for patients with clinically localized prostate cancer. Methods The clinical and pathologic data from 245 hormone-naive patients with clinical Stage T1c-T2cNxM0 prostate cancer who had undergone permanent prostate brachytherapy from 1992 to 2002 at our institution were retrospectively evaluated. The PPBs, preimplant prostate-specific antigen, and biopsy Gleason score were evaluated as predictors of BF after brachytherapy. The risk of BF was calculated using logistic regression models. The time to BF was assessed using Cox proportional hazard models and Kaplan-Meier estimates. Results The median PPBs in our study cohort was 27%. The risk of BF was 10.9% for those with a PPBs less than the median versus 26.2% for those with a PPBs greater than the median. A PPBs greater than the median was an independent predictor of BF on multivariate analysis (relative risk 2.3, 95% confidence interval 1.21 to 4.39, P = 0.011). In the time-to-failure models, the PPBs, prostate-specific antigen level, and Gleason score were significantly associated with BF. Conclusions Our data suggest that the PPBs is significantly associated with BF in patients undergoing permanent interstitial brachytherapy. The PPBs, along with the pretreatment prostate-specific antigen level and Gleason biopsy score, is a useful preoperative parameter in predicting for BF and the time to failure for patients treated with interstitial brachytherapy.