A simple method for estimating the optimum number of prostate biopsy cores needed to maintain high cancer detection rates while minimizing unnecessary biopsy sampling.

OBJECTIVE

The objective was to provide urologists with a simple basis for optimizing the number of prostate biopsy cores that should be taken.

METHODS

The records of 1024 patients who had undergone transrectal ultrasound-guided biopsies were reviewed. The prostate volume was divided by the number of biopsies to obtain the volume/biopsy ratio (VBR). Univariate and multivariate analyses were performed to determine the best predictors for positive biopsies.

RESULTS

The analysis included 939 patients who had prostatic-specific antigen <20 ng/mL. The significant independent variables for positive biopsies were age, prostatic-specific antigen, and prostate volume and VBR (p < 0.001). VBR had the strongest correlation coefficient out of all significant variables. Stepwise analysis showed a consistent increase in cancer detection rates as VBR was decreased. The detection rates for VBRs of 2, 3, and 4 were 59%, 53%, and 50%, respectively. The detection rates dropped sharply to 42% and 30% for VBRs of 5 and 6, respectively. Cancers diagnosed with low VBRs were similar to those diagnosed with high VBRs in regard to Gleason scores and percentages of cancer in the prostatectomy specimens.

CONCLUSION

Using VBR of 4 maintains high cancer detection rates without taking an excessive number of biopsy specimens. This is a simple and easy-to-remember method.