Purpose: We determine whether site specific labeling of sextant prostate biopsy cores predicts the site of extracapsular extension in a radical prostatectomy specimen, thereby justifying increased cost of pathological evaluation.
Materials and methods: Between January 1994 and December 1997, 407 radical prostatectomies were performed at our institution by a single surgeon (H. L.). Surgical specimens showing extracapsular extension were examined by a single pathologist (J. M.) to identify the site of extension. Several different methods of submitting transrectal ultrasound guided biopsy cores were used since the majority of cases did not undergo biopsy at our institution. In 243 cases sextant biopsies were labeled right versus left. Of these cases 103 specimen cores were individually labeled. The ability of the positive biopsy core location to predict the location of extracapsular extension in the surgical specimen was determined. Univariate and multivariate logistic regression analyses were performed to assess the ability of biopsy core characteristics, including Gleason score, percentage of cancer in the core, core location and number of positive cores in the specimen, to predict the site of extracapsular extension. A similar analysis was performed for the 243 cases with right versus left core labeling.
Results: The positive predictive value was 8.9+/-2.2% for a single positive core to identify the location of extracapsular extension correctly in the individually labeled core cases. The absence of cancer in a sextant biopsy had a negative predictive value of 96.9+/-1.4%. The overall sensitivity was 59.4+/-3.8% for a positive biopsy core. In the right versus left core cases the positive predictive value was 12.9+/-3.0% with a sensitivity of 85.1+/-3.2%. In an individual core Gleason score 8 or greater and/or cancer in more than 50% of tissue enhanced the positive predictive value but not to a clinically useful level. Multivariate logistic regression identified Gleason score, number of positive ipsilateral cores and base position of the positive biopsy as the most predictive variables for the site of extracapsular extension.
Conclusions: When submitting biopsy specimens by individually labeled core or right versus left core, the positive predictive value of an individual positive core for the location of extracapsular extension is not sufficient to guide the surgical decision to spare or excise a neurovascular bundle. Therefore, the clinical information provided by individually labeled or right versus left core labeling does not justify the increased associated costs.