Depth of mesorectal invasion has prognostic significance in T3N0 low rectal cancer.

Objective: To investigate mesorectal fat invasion as a prognostic factor for T3N0 low rectal adenocarcinoma following sharp mesorectal excision.

Methods: Subjects consisted of 26 patients who had a potential curative excision of a T3N0 low rectal adenocarcinoma without neoadjuvant therapy between August 1988 and April 2003. Histological preparations were used to measure depth of mesorectal invasion, which was analyzed for associations with disease-free survival and recurrence.

Results: Five-year overall survival and disease-free survival were 64.8% and 57.1%, respectively. Ten patients developed recurrent disease; 3 had local recurrence, 3 had distant metastasis, and 4 had both local and distant recurrence. Rectal cancers were stratified by depth of mesorectal invasion using 4 cutoff values (2, 3, 4, 5 mm), and examined by Cox proportional hazard model. At a cutoff of 3 mm, multivariate analyses confirmed depth of mesorectal invasion to be an independent prognostic factor for 5-year disease-free survival (< 3mm, 90.9%; > or = 3mm, 32.0%; p = 0.023). Distant metastasis differed significantly (< 3mm, 0%; > or = 3mm, 46.7%; p = 0.01), but local recurrence did not (< 3 mm, 9.1%; > or = 3mm, 40%; p = 0.17).

Conclusions: Patients with advanced low T3N0 rectal cancer are at high risk of distant metastases. Depth of mesorectal invasion may be valuable in decisions regarding intensive adjuvant therapy.