[Postoperative pathological staging correlates the prognosis of rectal cancer after neoadjuvant chemoradiotherapy].

Objective: The present study assessed the pathological staging features of rectal cancer after neoadjuvant chemoradiotherapy, and its relation to prognosis.

Methods: Pathologic data related to TNM classification were analyzed on the surgical specimens of 135 patients with mid-low rectal cancer after neoadjuvant themoradiotherapy from 2005 to 2012. Tumor invasion, nodal status, local invasive factors (including cancer deposit, radial margin, perivascular or perineural invasion) were investigated with patients' 3-year disease-free survival (DFS).

Results: The overall 3-year DFS was 85.2%, with a pathological complete response (pCR) rate of 19.26%. Three out of 29 patients (10.4%) with ypT0 were found to have positive lymph nodes. There was a trend towards decreased survival as the ypT category and ypTNM staging increased (χ(2) = 14.296 and 52.643, P = 0.006 and 0.000). ypT0-T2 in T category and yp0-I in TNM staging showed a favorable survival above 92%, while the patients with ypT3, or ypIIIB had a comparable lower DFS of 70.2% and 46.7%. DFS in patients with negative lymph node were significantly improved than those with positive nodes (93.5% vs. 66.7%, χ(2) = 34.125, P = 0.000). Patients with or without local invasive factor significantly differed in DFS (42.9% vs. 90.1%, χ(2) = 32.666, P = 0.000) . Cox regression analyze showed that the nodal status (RR = 12.312, 95%CI: 2.828-39.258, P = 0.000) and local invasive factors (RR = 5.422, 95%CI: 1.202-8.493, P = 0.020) were independent risk factors to 3-year survival. As the concept of clinical complete response (cCR) is obscure, there were 27.6% of patients with ypT0 had normal mucosa or no evidence of tumor by EUS or MRI tests before surgery.

Conclusion: Postoperative pathologic staging features were closely associated with patient's prognosis. The increasing of ypT or ypTNM staging was correlated to decreasing of DFS. Nodal status, positive radial margin, perivascular and perineural invasion were independent risk factors to DFS. Since cCR did not correlate and could not predict pCR, the ongoing radical surgery could not be avoided even there was no evidence of tumor existing before operation.