THE ROLE OF MR IMAGING IN DETERMINING SURGICAL ELIGIBILITY FOR PELVIC EXENTERATION

OBJECTIVE. The purpose of this study was to evaluate the role of MR imaging in the preoperative assessment of candidates for pelvic exenteration. Specifically, we sought to determine if MR imaging was reliable in selecting patients with pelvic cancer for surgical exenteration. MATERIALS AND METHODS. MR images of the pelvis were retrospectively evaluated in 23 patients with proved pelvic cancer. These images were analyzed for (1) presence and location of the primary or recurrent tumor; (2) tumor extension to the bladder, rectum, or pelvic sidewall; and (3) presence and location of lymphadenopathy. On the basis of the MR findings, we determined suitability for pelvic exenteration by using generally accepted contraindications to surgery (involvement of the pelvic sidewall muscles or metastatic lymphadenopathy). In addition, tumor involvement of the bladder or rectum was evaluated to help determine the type of exenteration indicated. Surgical and/or histologic confirmation was available in all 23 cases. RESULTS. The accuracy of MR imaging in selecting patients was 83% (19 of 23), with a positive predictive value of 56% and a negative predictive value of 100%. In evaluating tumor involvement of the pelvic sidewall and lymph nodes, the negative predictive values were 100% and 95%, respectively. Tumor extension into the pelvic sidewall was overestimated in four patients, in three of whom it was not possible to distinguish radiation changes from tumor on MR images. For assessing extension of these pelvic tumors into the bladder and rectum, MR imaging had an accuracy of 81% and 85%, respectively. CONCLUSION. MR imaging may provide an accurate means of selecting patients considered for pelvic exenteration. MR accurately determined which patients should undergo the surgery, by demonstrating absence of sidewall abnormalities or adenopathy. Radiation changes could not be reliably distinguished from tumor involvement in those patients with sidewall abnormalities, however, especially in the first 6 to 12 months after treatment.