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), χ² 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.

The Ratio of the Number of Biopsy Specimens to Prostate Volume (Biopsy Density) Greater Than 1.5 Improves the Prostate Cancer Detection Rate in Men Undergoing Transperineal Biopsy of the Prostate

PURPOSE

We sought to determine the minimum number of transperineal prostate mapping biopsies needed to optimize the prostate cancer detection rate.

MATERIALS AND METHODS

A total of 436 men underwent transperineal prostate mapping biopsy at 2 institutions. Biopsy density was calculated as the ratio of the total number of specimens retrieved (mean 59.4) to prostate volume (mean 44.9 cc). Associations of biopsy density with prostate specific antigen, prostate specific antigen density, cancer diagnosis and the Gleason score were tested by ANOVA and the chi-square test. Regression analysis was done to determine factors associated with a positive transperineal prostate mapping biopsy and Gleason score 7 or higher cancer.

RESULTS

Transperineal prostate mapping biopsy was positive in 299 of 436 men (68.6%). The mean number of positive cores was 7.1 (range 1 to 41) and mean biopsy density was 1.46 (range 0.39 to 3.67). The mean number of cores in positive vs negative transperineal prostate mapping biopsies was 1.61 vs 1.14 (p <0.001). Biopsy density cut points of 0.5 or less, greater than 0.5 to 1.0, greater than 1.0 to 1.5 and greater than 1.5 were associated with positive biopsy in 25%, 37.4%, 70.7% and 84.9% of patients (p <0.001). Dichotomizing biopsy density to 1.5 or less vs greater than 1.5 resulted in a positive biopsy rate of 56.4% vs 84.9% (OR 1.5, 95% CI 1.3-1.7, p <0.001). More Gleason score 6 cancers were diagnosed with higher biopsy density (94 of 158 or 59.5% vs 62 of 141 or 44.9%, p = 0.007). However, the number of positive cores with Gleason score 6 was greater in men with higher biopsy density at 4.9 vs 3.6 (p = 0.036). Prostate specific antigen (p = 0.053) and biopsy density (p = 0.012) were significant on regression analysis for positive transperineal prostate mapping biopsy and Gleason score 7+ disease.

CONCLUSIONS

Biopsy density greater than 1.5 increases the diagnosis of prostate cancer by 1.5 times, detects higher volume Gleason score 6 disease and should be considered the optimal sampling approach when performing transperineal prostate mapping biopsy.