Predicting unilateral prostate cancer on routine diagnostic biopsy: sextant vs extended

Objective: To compare the diagnostic properties of routine office-based sextant and extended biopsies for unilateral prostate cancer, as validated by final pathology, because focal therapy of prostate cancer is gaining acceptance as a viable treatment option and thus patient selection is of paramount consideration.

Patients and methods: We retrospectively analysed records of patients who had a radical prostatectomy (RP) for biopsy confirmed prostate cancer at our institution between 1990 and 2007. Records with incomplete data were excluded. Diagnostic properties for sextant and extended biopsies were calculated and compared for diagnostic accuracy, sensitivity, specificity, positive and negative predictive values (PPV, NPV) and false-positive and -negative rates.

Results: We identified 882 records (729 sextant, 153 extended biopsies) matching our criteria. Overall, unilateral prostate cancer was confirmed in 151 (16%) of pathological RP specimens. The sensitivity improved from 84.1% to 88.0% on sextant and extended biopsy, respectively. Similarly, the PPV increased from 21.9% to 27.2%, specificity from 37.1% to 53.9% (P < 0.05), and NPV from 91.8% to 95.8% (P < 0.05). These changes are reflected in the decrease in false-positive rates (from 62.9% to 46.1%) and false-negative rates (from 15.9% to 12.0%). The overall diagnostic accuracy increased from 49% on sextant to 59% on extended biopsy (P < 0.05).

Conclusions: Taking more prostate biopsy cores improves the diagnostic properties for identifying unilateral prostate cancer. However, a 12-core biopsy is not an ideal diagnostic test to select patients for focal therapy, and should be interpreted in conjunction with imaging and clinical variables. Additional research should investigate the diagnostic gain associated with a further increase in the number of biopsy cores.