ENDORECTAL ULTRASOUND OF T3 AND T4 RECTAL CANCERS AFTER PREOPERATIVE CHEMORADIATION

PURPOSE: This study was undertaken to assess the accuracy and ability of endorectal ultasound (ERUS) to predict changes in rectal tumor stag e after a preoperative chemo-radiation protocol. METHODS::Since Decemb er 1990, all rectal malignancies at our institution have been preopera tively staged with ERUS. ERUS has been an essential tool in preoperati ve staging of rectal cancer patients, possessing an overall accuracy o f 84 percent for T stage and 81 percent for lymph node status in our h ands (Williamson PR, unpublished data). Beginning in July 1992, all pa tients staged with T3 or T4 lesions on initial ERUS have been entered into a protocol consisting of preoperative chemoradiation therapy (CRT ). This protocol consists of patients receiving 4,500 to 5,040 rads fo r five to eight weeks and concomitantly receiving sensitizing doses of 5-fluorouracil and/or leucovorin. All patients were scheduled for sph incter-saving or abdominoperineal resections six to eight weeks follow ing completion of CRT. A repeat ERUS was performed on each patient one week before surgery. RESULTS: The study group consisted of 15 patient s who completed CRT, including 12 males and 3 females. Evidence of tum or shrinkage via ERUS measurement was seen in all patients. Average tu mor shrinkage as assessed by ERUS was 16 percent by width and 32 perce nt by depth of invasion. Sonographic level of invasion and nodal statu s were each downstaged in 38 percent of patients. Pathologic evaluatio n comparison revealed that the level of invasion was downstaged in 47 percent and nodal status in 88 percent compared with initial ERUS stag ing. Of those patients downstaged, 4 of 11 (36 percent) revealed no tu mor in the pathology specimen. CONCLUSIONS: We conclude from our early experience that although ERUS offers a method for assessing degree of shrinkage and down-staging of T3 and T4 lesions after CRT, presently it does not closely predict the pathologic results. Results are strong ly related to the experience of the ultrasonographer. The ability to d istinguish tumor from radiation-induced changes to perirectal tissues is under continued investigation, and a new method of interpreting the data obtained by ERUS after CRT will need to be established.