Endorectal ultrasound for control of preoperative radiotherapy of rectal cancer.

Endorectal ultrasound (EUS) is known to be a reliable method for preoperative staging of rectal tumors. In this study, EUS was used to select patients with rectal cancer suitable for preoperative radiation therapy. By performing EUS before and after radiation, the aim of the study was to evaluate the role of EUS in monitoring the effects of preoperative radiation therapy. In 17 patients with large T3 or T4 rectal tumors, a complete staging by EUS was done before and after radiation therapy. Beside a shrinkage of the tumor, there was a change of echopattern to more hyperechoic gray levels to be observed in the irradiated tumor. The rectal wall lost its normal architecture, and lymph nodes disappeared or changed their echopattern from echopoor to echorich. There was no down-staging of a tumor seen by EUS. Complete preoperative staging was correct in 13 of 17 patients because of endosonographic examination before and after preoperative radiation therapy. New interpretation criteria are given for evaluation of patients with rectal cancer treated by radiation therapy.