Can rectal cancers with pathologic T0 after neoadjuvant chemoradiation (ypT0) be treated by transanal excision alone?

Background: Patients with rectal cancer who have complete rectal wall tumor regression after neoadjuvant chemoradiation probably have eradication of tumor cells in the mesorectum as well, thus raising the possibility of transanal excision. Methods: All pathology reports of all patients with locally advanced low and mid rectal cancer who underwent preoperative chemoradiation followed by radical resection from May 2000 to June 2004 were reviewed to evaluate the correlation between complete tumor response (ypT0) and nodal response. Results: One hundred one consecutive patients had neoadjuvant chemoradiation followed by definitive operation. Four were excluded, leaving 64 men and 33 women (median age, 62 years). Fifty-three patients (55%) had mid rectal cancer, and 44 (45%) had low rectal cancer. Fifty-eight patients (60%) underwent low anterior resection, and 36 (37%) underwent abdominoperineal resection. In 17 patients (18%), no residual tumor cells were present within the rectal wall. One patient (6%) with ypT0 disease had positive lymph nodes. Conclusions: No residual tumor in the rectal wall correlates with the absence of viable cancer cells in the mesorectal tissue (94%). Approximately 10% of T1 tumors have involved lymph nodes, and local excision is an accepted option. Transanal excision could probably be considered in a highly selected group of patients with a mural pathologic complete response to neoadjuvant therapy. This approach should be prospectively investigated, and strict selection guidelines should be used.