It is controversial whether tumor extent in radical prostatectomies predicts biochemical recurrence following surgery. We compared the predictive value of total tumor extent vs dominant nodule (index tumor) extent. A mean of 32 paraffin blocks was processed from prostate surgical specimens step sectioned at 3 to 5 mm intervals from 300 patients treated with radical retropubic prostatectomy. Each transverse section was subdivided into 2 anterolateral and 2 posterolateral quadrants. Tumor extent was evaluated by a semiquantitative point count method. Dominant nodule extent was recorded as the maximal number of positive points of the largest single focus of cancer in the quadrants. Time to biochemical recurrence was analyzed by Kaplan-Meier product limit analysis. Prediction of shorter time to biochemical recurrence was determined by univariate and multivariate Cox proportional hazards models. Except for age and race, total and index tumor extent was significantly associated with higher preoperative prostate specific antigen, clinical stage T2, pathological stage greater than T2, positive surgical margins and higher radical prostatectomy Gleason score. Total and index tumor extent was significantly associated with time to biochemical recurrence in Kaplan-Meier estimates. Total and index tumor extent significantly predicted shorter time to biochemical recurrence on univariate analysis but only index tumor extent was an independent predictor of time to biochemical recurrence on multivariate analysis. The study indicates that any tumor extent estimate in surgical specimens should be related to the dominant nodule (index tumor) and not to total tumor extent.18999-104