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OBJECTIVES - To examine the relationship between the percentage of positive biopsies (PPBs) and freedom from biochemical recurrence (FFBR) in men treated with low-dose-rate prostate brachytherapy (LDRPB) alone. The PPBs has been associated with FFBR in men treated with radical prostatectomy and external beam radiotherapy for prostate cancer.
METHODS - This report concerns 108 men treated with LDRPB alone between November 1997 and December 1999. All patients had clinically localized prostate cancer confirmed by biopsy. All men were treated with iodine-125 to 144 Gy. FFBR was estimated using the product-limit method. Putative covariates for FFBR, including T stage, Gleason score, pretreatment prostate-specific antigen level, minimal dose received by 90% of the target volume, and PPBs, were examined using the proportional hazards regression model.
RESULTS - The median follow-up was 61 months. Of the 108 men, 13 developed evidence of biochemical relapse at a median of 25 months. The 5-year estimate of FFBR was 87% (95% confidence interval 81% to 93%) for the entire cohort. On univariate analysis, prostate-specific antigen, T stage, minimal dose received by 90% of the target volume, and PPBs were associated with FFBR. In the multivariate model, the PPBs was the only variable that predicted for FFBR (P = 0.002). The 5-year estimate of FFBR was 95% for patients with less than 50% PPB disease versus 63% in patients with more than 50% PPB disease (P < 0.0001).
CONCLUSIONS - The PPBs is an important independent predictor of FFBR after LDRPB alone. The FFBR after LDRPB in the group of patients with more than 50% PPBs was poor.