Extraprostatic Spread of Clinically Localized Prostate Cancer: Factors Predictive of pT3 Tumor and of Positive Endorectal MR Imaging Examination Results

PURPOSE: To identify the factor(s) most predictive of pT3 tumor and those most predictive of a positive endorectal magnetic resonance (MR) imaging result in patients with clinically localized prostate cancer. MATERIALS AND METHODS: At multivariate analysis, five preoperative clinical parameters-prostate-specific antigen (PSA) level, digital rectal examination (DRE) result, Gleason score and number of involved sextants at transrectal US-guided biopsy, and endorectal MR imaging result-were used to predict pT3 tumor in 336 patients who underwent radical prostatectomy. On the basis of results of the first four examinations, multivariate analysis was performed also to determine predictors of a positive MR imaging study. RESULTS: Significant predictors of pT3 tumor were positive MR imaging result (P < 2 x 10(-8)), more than one sextant involved at biopsy (P < 5 x 10(-5)), and PSA level greater than 10 ng/mL (P < 7 x 10(-3)). Significant predictors of a positive MR imaging result were three or more sextants involved at biopsy (P < 10(-5)), positive DRE result (P < 5 x 10(-3)), and PSA level greater than 10 ng/mL (P < 16 x 10(-3)). In the subgroup of 175 patients who had at least three positive biopsy specimens, the sensitivity of MR imaging was 50% for detection of occult pT3 tumor and 69% for detection of extensive pT3 tumor. The overall specificity of MR imaging was 95%. CONCLUSION: Endorectal MR imaging seems to be indicated in carefully selected patients-specifically, those with three or more positive biopsy specimens, a palpable tumor, and/or a PSA level greater than 10 ng/mL.