Mesorectal Invasion Depth in Rectal Carcinoma Is Associated With Low Survival

Abstract Background Most cases of rectal cancer (RC) in our institution are in pathologic stage T3. They are a heterogeneous group but have been classified in a single-stage category. We performed the present study to validate the prognostic significance of the mesorectal extension depth (MED) in T3 RC measured in millimeters beyond the muscularis propria plane. Materials and Methods We performed a retrospective analysis of 104 patients with T3 RC who had undergone curative surgery after a course of preoperative chemoradiotherapy at a tertiary referral cancer hospital. The patients were grouped by MED (T3a,  5-10 mm; and T3d u003e 10 mm). The clinicopathologic data and disease-free survival were analyzed. Results The 5-year disease-free survival rate according to the T3 subclassification was 87.5% for those with T3a, 57.9% for T3b, 38.7% for T3c, and 40.3% for those with T3d tumors ( P  = .050). On univariate and multivariate analysis, the prognostic factors affecting survival were overall recurrence (hazard ratio [HR], 3.670; 95% confidence interval [CI], 1.710-7.837; P  = .001), histologic grade (HR, 2.204; 95% CI, 1.156-4.199; P  = .016), mesorectal invasion depth (HR, 1.885; 95% CI, 1.164-3.052; P  = .010), and lymph node metastasis (HR, 1.211; 95% CI, 1.015-1.444; P  = .033). Conclusion MED is a significant prognostic factor in patients with T3 RC who have undergone neoadjuvant chemoradiotherapy, especially when the MED is u003e 5 mm. The MED could be as important as other clinicopathologic factors in predicting disease-specific survival.