Significance of Predicted Tumor Volume as a Predictor of Pathologic Stage in Patients Undergoing Radical Prostatectomy

PURPOSE The purpose of this study was to evaluate whether predicted tumor volume could predict pathologic stage in patients undergoing radical prostatectomy. MATERIALS AND METHODS The clinical and pathologic data of 236 patients who underwent a 12-core needle biopsy followed by radical prostatectomy were obtained from our database and reviewed retrospectively. RESULTS Observed tumor volume correlated best with serum prostate-specific antigen (PSA) level (r=0.677, p<0.001) and the number of positive biopsy cores (r=0.489, p<0.001). Stepwise multiple linear regression analysis was used to develop a model for predicting tumor volume before radical prostatectomy. All explanatory variables except PSA and the number of positive biopsy cores were eliminated, yielding the equation ([predicted tumor volume]=0.381x[PSA]+0.921x[No. of positive biopsy cores]-0.992). Tumor volume predicted by this equation correlated strongly with observed tumor volume (r=0.722, p<0.001). This was also true when a different cohort of 159 patients was analyzed (r=0.638, p<0.001). The areas under the receiver operating characteristic curves of predicted tumor volume were 68.5% for extracapsular extension, 75.7% for seminal vesicle invasion, and 70.4% for positive surgical margin. Kaplan-Meier curves revealed that predicted tumor volume correlated significantly with biochemical recurrence-free survival (p<0.001; log-rank test). CONCLUSIONS Our findings suggest that tumor volume predicted on the basis of PSA levels and number of positive biopsy cores may predict pathologic stage with reasonable accuracy.