Patterns of residual disease after preoperative chemoradiation in ultrasound T3 rectal carcinoma

Rectal carcinoma tends to recur locally, with invasion of adjacent organs and significant pelvic pain. Both radiation therapy alone and combined chemoradiation have been used in an attempt to decrease the local recurrence rate and thereby improve survival. Although preoperative chemoradiation can clinically downstage rectal tumors, the pathologic extent of the residual disease has not been studied.

Thirty-seven patients with T3 rectal cancer diagnosed by transrectal ultrasonography (uT3) received 45 Gy with continuous infusion 5-fluorouracil (300 mg/m2/day). Proctoscopy with mucosal/submucosal biopsy was performed in patients (16 of 37) posttreatment and before definitive surgery.

Microscopic evaluation of the 37 resected specimens showed a 30% (11 patients) pathologic complete remission rate. The pattern of residual disease in the remaining 26 patients showed that nine (25%) had microscopic residual tumor without evidence of mucosal involvement. Of the 14 patients with a negative proctoscopic evaluation and biopsy only, five (36%) had no residual tumor on final pathology.

After chemoradiation, the pathologic presentation of rectal cancer may be altered, making endoscopic procedures and mucosal/submucosal biopsies unreliable in detection of residual disease. Despite the relatively good pathologic complete remission rate noted in this study, all patients undergoing chemoradiation for uT3 rectal carcinomas need definitive surgical resection to confirm a complete clinical remission.