Prediction of tumour volume and pathological stage in radical prostatectomy specimens is not improved by taking more prostate needle-biopsy cores.

OBJECTIVE

To determine what, if any, additional prognostic information is available from the prostate needle biopsy by comparing the number of biopsy cores obtained with the pathology assessed from the radical retropubic prostatectomy (RRP) specimen.

PATIENTS AND METHODS

The results from 135 consecutive patients who underwent RRP at a single institution were reviewed. Needle biopsy information (number of cores, percentage of positive cores, laterality of the positive cores, and Gleason sum) were compared with the pathological data of the RRP specimen, including stage, Gleason sum and tumour volume. Patients were further stratified into those with six or fewer cores (96 men) or more than six cores (39 men). Clinical data, including biopsy information and pathological findings, were compared using univariate and multivariate models.

RESULTS

Overall, univariate analysis showed that the total prostate-specific antigen (PSA) level, number of positive cores, bilateral positive cores and percentage of positive cores were directly correlated with tumour volume (P=0.01). Also, PSA and percentage of positive cores were directly correlated with extracapsular extension (P=0.008 and P=0.01, respectively). In the multivariate model, the most important independent predictors of RRP tumour volume and pathological stage were the preoperative PSA level and percentage of cancer in the biopsy (P<0.01). There was no significant relationship between the number of cores obtained and the predicted pathology of the RRP specimen. There were no differences in the number of positive cores, bilateral positive cores or percentage tumour in the cores between men with more or less than six biopsies. In men with more than six core biopsies, there was no significant increase in prognostic information for tumour volume and extracapsular extension, or a correlation between the Gleason sum on biopsy and the RRP specimen. Taking more than six biopsies did not result in a significantly greater detection of potentially indolent tumours (defined as a tumour volume of <0.5 mL).

CONCLUSIONS

While taking more prostate needle biopsy cores seems to improve the detection of prostate cancer, there appears to be no major improvement in prognostic information over that gained from traditional sextant biopsies. Furthermore, the results suggest that the percentage of positive cores is the best predictor of both pathological stage and tumour volume, from among the information readily available from prostate needle biopsy. Given the variability in the number of cores obtained for diagnosis in clinical practice, these results add credence to the use of the percentage of positive cores in the biopsy set, with known predictors such as PSA and Gleason score, into future models that attempt to predict tumour biology.