Comparison of 12-core versus 8-core prostate biopsy: multivariate analysis of large series of US veterans.

ABSTRACT

OBJECTIVES: To investigate the impact of additional biopsy cores on prostate cancer diagnosis among US veterans. The reported rate of positive biopsy results varies from 20% to 40%. METHODS: We analyzed 1546 consecutive initial prostate biopsy procedures (8-core and 12-core biopsy protocols) at the Atlanta VA Medical Center. Both biopsy protocols targeted the peripheral zone. Cancer detection rates were compared between the 2 protocols in univariate and multivariate analyses with results expressed as odds ratios and corresponding 95% confidence intervals. Characteristics of cancer detected were also compared. Sensitivity analyses were performed for different population subgroups. RESULTS: The overall positive biopsy rate was 49.9%, 51.2% in the 8-core group and 49.2% in the 12-core group. There was no difference between the 2 biopsy groups (adjusted odds ratio = 0.97, 95% confidence interval = 0.76-1.25). Advanced age and high body mass index were significantly associated with higher likelihood of prostate cancer, whereas larger prostate volumes were associated with lower risk. CONCLUSIONS: In this large series of prostate biopsy procedures, in which the peripheral zone was well targeted, there was no evidence that 12-core biopsy improved the likelihood of prostate cancer diagnosis compared with 8-core biopsy. As such, the results of this cohort from a US veteran population suggest that targeting the peripheral zone is more important than the absolute number of biopsy cores. However, in certain subgroups of patients with specific clinical characteristics, such as those with very large prostates, more cores may be required. Further studies are needed to identify such characteristics.