Prostate sampling by 12-core biopsy: comparison of the biopsy results with tumor location in prostatectomy specimens

To analyze the diagnostic performance of individual prostate biopsy cores. The 12-core transrectal prostate biopsy scheme has emerged as a standard of care. However, quality of sampling may vary in different areas of the prostate included in this procedure.

Two-hundred fifty men underwent radical prostatectomy at our institution. All participants had a systematic 12-core transrectal prostate biopsy containing lateral and medial cores from each side of the apical, medial and basal thirds of the prostate. Biopsy results were matched with histologic maps of the prostatectomy specimens. Sensitivity, negative predictive value (NPV), and overall accuracy were calculated for each biopsy core location and compared between different groups of cores. In addition, patients in the upper quartile of prostate weight were compared with the rest of the cohort.

Sensitivity, NPV, and overall accuracy were significantly lower for apical cores. Average NPV and overall accuracy of basal and mid-lateral biopsies were inferior to those of medial biopsies on the same levels. However, sensitivity of these lateral cores was similar to that of the medial cores. Sensitivities of apical and mid cores were significantly lower in patients with larger prostates.

Decreased accuracy in lateral mid- and basal cores results from higher frequencies of cancer in corresponding prostate areas, and therefore additional samples should be taken at these locations. In addition, diagnostic accuracy of apical cores may be improved through better targeting of the prostatic apex. This may be particularly important in patients with larger prostates.