Long-term Outcome Of Neoadjuvant Chemoradiotherapy Based On Depth Of Invasion In MrT₃ Low Rectal Cancer

Objective To investigate the prognosis of c T3 and the subgroups of low rectal cancer who underwent neoadjuvant chemoradiotherapy(CRT), whether shell all patients with c T3 low rectal cancer undergo CRT.Methods Retrospective analysis of 223 patients with c T3 low rectal cancer who were treated in the Department of Colorectal Surgery in Fujian Medical University Union Hospital from January 2008 to December 2012, which was assigned into three subgroups(mr T3 a, mr T3 b, and mr T3c) according to The Radiologic Society of North America(RSNA) proposal criteria by measuring the depth of mesorectal invasion(DMI)(< 5, 5–10, and > 10 mm), and according to whether underwent CRT divided into neoadjuvant chemoradiotherapy group(CRT group)(115 cases) and no underwent neoadjuvant chemoradiotherapy group(n CRT group)(108 cases), Compare the prognosis of the two groups and their subgroups(mr T3 a mr T3 b mr T3c).Results 1. The overall accuracy of MRI for stratifying subgroups was 70.4%(76/108); 2.The depth of tumor invasion(T3a, T3 b and T3c) has a correlated significantly with neoadjuvant chemotherapy response and tumor regression grade(r = 0.277, P = 0.003; r = 0.339, P = 0.000); 3. The CRT and n CRT groups revealed no significant differences in the 3-year disease-free survival rate and the local recurrence rate for all the mr T3 patients(78.2% vs. 71.9%, P=0.608; 4.4% vs. 8.5%, P=0.120) and mr T3 a patients(82.4% vs. 81.8%, P=0.837; 5.8% vs. 5.9%, P=0.658). On the contrary, for the mr T3 b patients, the CRT and n CRT groups revealed significant differences in the 3-year disease-free survival rate(84.4% vs. 42.4%, P=0.032) and local recurrence rate(0.0% vs. 18.2%, P=0.014). For the mr T3 b,c patients, the CRT and n CRT groups revealed no significant difference in the 3-year disease-free survival rate(72.8% vs. 42.4%, P=0.060) but revealed a significant difference in the local recurrence rate(2.4% vs. 18.2 %, P=0.021). COX regression analysiswas utilized for 3-year disease-free survival, DMI and circumferential resection margin(CRM) were significant in the univariate analysis.Additionally, the multivariate analysis indicated that CRM is an independent impact factor(OR=2.249, CI 1.067-4.742, P=0.033).Conclusions 1. MRI can be used for prognostic stratification according to extramural depth of tumor invasion based on the RSNA proposal for patients with T3 rectal cancer.;2.CRT can improve the prognosis of patients with mr T3 b,c low rectal cancer, but may not significantly influence the prognosis of patients with mr T3 a and CRM-negative low rectal cancer, surgical treatment can be performed in these patients without CRT.