Does the depth of mesorectal invasion have prognostic significance in patients with ypT3 lower rectal cancer treated with preoperative chemoradiotherapy?

The prognostic significance of the depth of mesorectal invasion (DMI) in patients with ypT3 rectal cancer who undergo preoperative chemoradiotherapy (CRT) is unclear. The purpose of this study was to evaluate the prognostic significance of DMI in ypT3 rectal cancer. A total of 168 (y)pT3 patients were evaluated, of whom 93 received preoperative CRT and 75 underwent surgery alone. Patients were subdivided into two groups according to the DMI (T3ab = DMI ae<currency>5 mm and T3cd = DMI > 5 mm). Oncologic outcomes were compared between the T3ab and T3cd groups and the ypT3ab and ypT3cd groups. Relapse-free survival was significantly different between the pT3ab and pT3cd groups (74.1 vs 38.5%, P = 0.0192) but not between the ypT3ab and ypT3cd groups (65.9 vs 61.5%, P = 0.513). Multivariate analysis showed that DMI was an independent predictor of recurrence in pT3 patients (hazard ratio [HR] = 2.980, 95% confidence interval [CI] 1.227-7.025; P = 0.0169) and that ypN+ was an independent predictor of recurrence in ypT3 patients (HR = 3.487, 95% CI 1.570-8.827; P = 0.0016). DMI was not a significant predictive factor for recurrence in patients with ypT3 rectal cancer who underwent preoperative CRT, and ypN+ was the only independent predictive factor for recurrence.