Value of ultrasound-guided systematic sextant biopsies in prostate tumor mapping

Objective: To determine the value of positive sextant biopsies in assessing the location of prostate tumors within radical prostatectomy specimens and to determine if prostate weight influences the results. Methods: From 1988 to 1996, 166 radical prostatectomies were performed for localized prostate cancer diagnosed by means of ultrasound-guided sextant biopsies. The location of the biopsies was compared with that of tumor tissue within the radical prostatectomy specimen. Results: Of the 996 biopsies, 331 (33%) were positive. The correspondence between the location of the biopsies and that of tumor tissue in the surgical specimen was found to have a sensitivity of 39.4%, a specificity of 81.5%, a positive predictive value of 83.3%, negative predictive value of 36.4% and an accuracy of 52%. For prostates weighing < and greater than or equal to 45 g, the sensitivity was 39.9 and 38.9%, the specificity was 88 and 77.2%, the positive predictive value was 90.8 and 76.1%, the negative predictive value was 34.9 and 39.8%, and the accuracy was 52 and 52%, respectively. Conclusion: Negative biopsies do not predict a lack of tumor tissue in the corresponding prostate site after radical prostatectomy, and had less value than positive biopsies for prognostic staging before radical prostatectomy. Results of sextant biopsies are more significant for prognosis before radical prostatectomy when positive. Prostate weight influences the interpretation of the results of sextant biopsies.