LOCAL STAGING OF PROSTATE-CANCER WITH ENDORECTAL MR-IMAGING - CORRELATION WITH HISTOPATHOLOGY

OBJECTIVE. To evaluate the accuracy of MR imaging of the prostate with an endorectal surface coil in determining presence, localization, vol ume, and local stage of prostate carcinoma. SUBJECTS AND METHODS. MR i mages of 34 patients with biopsy-proven cancer were correlated retrosp ectively with the histologic mappings of radical prostatectomy specime ns, The volume and number of tumor lesions on MR images were calculate d and compared with the surgical specimens used as the gold standard, Tumor stage based on MR imaging was compared with the pathologic stage according to the TNM classification, Predictive values were calculate d separately for all lesions and for the lesions correctly localized w ith MR imaging. RESULTS. MR imaging correctly depicted the location of 67% of the tumors, Twenty percent of the lesions depicted by MR imagi ng appeared to be false-positive errors, The tumors that were missed w ere located centrally and ventrally in the prostate, Tumor volume as s hown by MR imaging was within a 25% range of the actual tumor volume i n 10 cases, overestimated in 16 cases, and underestimated in eight cas es, Histopathology showed capsular penetration in 12 of 34 patients (3 5%) and in 14 of 52 lesions (27%), Sensitivity, specificity, and posit ive predictive values were 43%, 84%, and 55%, respectively, Histologic ally, capsular penetration extended less than 1 mm into the periprosta tic adipose tissue in seven patients. Sensitivity for capsular penetra tion less than 1 mm was 14%, Sensitivity for capsular penetration more than 1 mm was 71%, Accuracy for differentiating a pT2 from a pT3 tumo r was 68%. CONCLUSION. Results from this study indicate that the accur acy of the technique was not satisfactory for predicting actual tumor volume, Tumor detection and localization was more accurate in the peri pheral zone than in the central zone, Accuracy was poor for detecting capsular penetration of less than 1 mm, but accuracy was much better f or penetration of more than 1 mm, Because recent reports suggest that capsular penetration of less than 1 mm does not adversely affect surgi cal cure, MR imaging still may be practical in the selection of patien ts for radical prostatectomy.