The potential impact of prostate volume in the planning of optimal number of cores in the systematic transperineal prostate biopsy

OBJECTIVES: We compared the detection rates of different transperineal prostate biopsy protocols with the aim to optimize the number of cores to sample according to prostate volume. MATERIAL AND METHODS: From October 2002 to October 2004 we evaluated 480 consecutive patients with PSA between 2.5 and 20 ng/ml undergoing the first set of prostate biopsy. All patients underwent a 14-core TRUS-guided transperineal prostate biopsy, including 12 cores in the peripheral and two in the transitional zone. The detection rate of the 14-core scheme was compared to the one of the other biopsy schemes obtained through the exclusion of pairs of cores. Data were stratified according to the different TRUS estimated prostate volumes. RESULTS: The detection rate of the standard sextant was 35.2%, while those of the 8-core schemes ranged from 37.1 to 38.8%. The 10-core schemes yielded detection rates of 39.6-40.8% and the protocol with 12 biopsies in the peripheral zone diagnosed prostate cancer in 42.1% of the patients. In patients with <30 cc prostate volume, the detection rate of the 14-core scheme was 43.8% and resulted statistically overlapping to the 8-peripheral cores protocol. In patients with 30.1-50 cc prostate volume a 12-peripheral core biopsy reproduced the results of the 14-core sampling. In prostates larger than 50 cc, an even more extensive procedure was mandatory, considering the low detection rate of the 14-core scheme (24.2%). CONCLUSION: Transperineal prostate biopsy is a safe procedure with a very low complication rate and high cancer detection rate. Prostate volume is the most relevant variable in the planning of the optimal number of cores in the extensive first biopsy set. A protocol with more than 8 peripheral cores) is recommended only in patients with prostate volume larger than 30 cc.