Submucosal infiltration and local recurrence in pT1 low-risk rectal cancer treated by transanal endoscopic microsurgery

Background: The association between submucosal infiltration and tumor recurrence was analyzed by long-term follow-up of patients with pT1 "low risk" rectal carcinoma.

Methods: Forty patients with pT1 rectal cancer of the upper and middle rectum were treated by transanal endoscopic microsurgery. All carcinomas fulfilled the low-risk criteria, and were completely resected. No further treatment was carried out. Follow-up data were available for all 40 patients, with a median follow-up of 5.4 years.

Results: Two patients (5.0%) developed local tumor recurrence after 14 and 18 months, respectively, and had curative rectal resection after neoadjuvant radiochemotherapy. In the histology of the initial specimens, both patients had deep submucosal infiltration (sm3). Another patient, primarily sm2 without local recurrence, developed a metachronous singular liver metastasis which was curatively resected. The risk of developing a recurrent tumor was significant for sm3 carcinomas (sm1+sm2 vs sm3, P=0.046).

Conclusions: Transanal endoscopic microsurgery is an excellent method of treating low-risk pT1 carcinomas of the rectum. Deep submucosal infiltration (sm3) seems to be an additional high-risk factor for developing local recurrence.