Author(s): Zmora O, Dasilva GM, Gurland B
Abstract PURPOSE: Preoperative chemoradiation may downstage locally advanced rectal cancer and, in some cases, with no residual tumor. The management of complete response is controversial and recent data suggest that radical surgery may be avoided in selected cases. Transanal excision of the scar may determine the rectal wall response to chemoradiation. This study was designed to assess whether the absence of tumor in the bowel wall corresponds to the absence of tumor in the mesorectum, known as true complete response. METHODS: A retrospective review of the medical records of patients who underwent preoperative chemoradiation for advanced mid (6-11 cm from the anal verge) and low (from the dentate line to 5 cm from the anal verge) rectal cancer (uT2-uT3) followed by radical surgery with total mesorectal excision was undertaken. Patients in whom the pathology specimen showed no residual tumor in the rectal wall (yT0, "y" signifies pathologic staging in postradiation patients) were assessed for tumoral involvement of the mesorectum. RESULTS: A total of 109 patients underwent preoperative, high-dose radiation therapy (94 percent with 5-fluorouracil chemosensitization), followed by radical surgery for advanced rectal cancer. Preoperatively, 47 patients were clinically assessed to have potentially complete response. After radical rectal resection, pathology did not reveal any residual tumor within the rectal wall (yT0) in 17 patients. In two (12 percent) of these patients, the mesorectum was found to be positive for malignancy: one had positive lymph nodes that harbored cancer; one had tumor deposits in the mesorectal tissue. CONCLUSIONS: Compete rectal wall tumor eradication does not necessarily imply complete response, because the mesorectum may harbor tumor cells. Thus, caution should be exercised when considering the avoidance of radical surgery. Reliable imaging methods and clinical predictors for favorable outcome are important to allow less radical approaches in the future.