Transperineal mapping biopsy improves selection of brachytherapy boost for men with localized prostate cancer.

Purpose: To determine if transperineal mapping biopsy (TPMB) can improve the selection of brachytherapy alone (BT) or brachytherapy boost (BTB) in men with localized prostate cancer.

Methods And Materials: Two hundred and eighteen men underwent TPMB with a mean of 48.6 cores retrieved. Comparisons were made between prebiopsy risk features and biopsy results to treatment choice with associations tested with ANOVA (bootstrap), χ test (Pearson), and linear regression. Survival estimates were tested by the Kaplan-Meier method with comparisons by log rank.

Results: Mean age, prostate specific antigen (PSA), prostate specific antigen density (PSAD), and prostate volume were 67.2 years, 8.1 ng/mL, 0.19, and 50.3 cc, respectively. 105 (48.2%) biopsies were positive for Gleason Group (GG) 1: 34 (32.4%), 2: 21 (20%), 3: 31 (29.5%), 4: 7 (6.7%), and 5: 12 (11.4%). The mean number of positive cores (PCs) was 7.3 (median 6, range 1-37). Men with six or more PCs had higher PSA (11.3 vs. 6.0 ng/mL, p = 0.025) and PSAD (0.34 vs. 0.13, p = 0.013). Overall brachytherapy was used in 74 (70.5%) as either monotherapy or boost therapy. Men with BTB had higher PSA (9.7 vs. 6.7 ng/mL, p = 0.029), PSAD (0.27 vs. 0.16, p = 0.007), GG (3.3 vs. 1.8, p < 0.001), more bilateral disease (75.9% vs. 55.6%, odds ratio 3.9, p = 0.008), and PCs (10.9 vs. 4.4, p < 0.001). On linear regression, only GG (p = 0.008) and PCs (p = 0.044) were associated with BTB. Biochemical-free failure at 5 years was 92.7%.

Conclusions: TPMB improves the selection of patients for BTB. Men with more PCs are more likely to have BTB. Restricting the need for BTB to those with greater volume prostate cancer may reduce radiation side effects.