To evaluate whether the maximal tumor diameter (MTD) is significantly associated with the time to postoperative prostate-specific antigen (PSA) failure.

Between 1986 and 2002, 781 men with clinical Stage T1c–T2 prostate cancer underwent radical prostatectomy. The MTD was recorded as the maximal dimension of the largest single focus of cancer from all 3-mm step sections. The median follow-up was 5.4 years (range 0.1 to 14.9); 242 men (31%) experienced PSA failure. A Cox regression analysis was used to determine the predictors of time to postoperative PSA failure. Kaplan-Meier estimates of PSA failure-free survival were made, dichotomized about the median MTD value, and compared using a two-sided log-rank test.

The value of the MTD was significantly associated with the time to PSA failure (adjusted hazard ratio 1.04, 95% confidence interval 1.01 to 1.07, P = 0.004), controlling for preoperative PSA level (P <0.0001), prostatectomy Gleason score (P <0.0001), and T stage (P <0.0001). When margin status was added (P = 0.0004), the MTD approached statistical significance (P = 0.07). For patients with a preoperative PSA level of less than 10 ng/mL, prostatectomy Gleason score of 3 + 4 = 7 or less, Stage pT2–T3a, and negative margins, the value of the MTD significantly (P = 0.05) stratified the time to PSA failure, when dichotomized about the median value (13 mm), with 7-year PSA failure estimates of 17% versus 8%.

Whether patients with traditionally low-risk but large MTD prostate cancer fare better when treated with adjuvant radiotherapy compared with salvage radiotherapy remains to be answered in the setting of a randomized trial.