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.