Prognostic value of pathological node status after neoadjuvant radiotherapy for rectal cancer

Abstract

Background: The prognostic value of pathological lymph node status following neoadjuvant radiotherapy (ypN) remains unclear. This study was designed to determine whether ypN status predicted overall survival.

Methods: Patients with locally advanced rectal adenocarcinoma who underwent neoadjuvant long-course radiation between 2005 and 2014 were identified from the National Cancer Data Base, and divided into ypN0, ypN1 and ypN2 groups. The primary outcome was overall survival. Univariable and multivariable analyses were used to determine factors associated with overall survival.

Results: Of 12 271 patients, 3713 (30·3 per cent) were found to have residual nodal positivity. A majority of patients with ypN1 (1663 of 2562) and ypN2 (878 of 1151) disease had suspected lymph node-positive disease before neoadjuvant therapy, compared with 3959 of 8558 with ypN0 tumours (P < 0·001). Moreover, ypN1 and ypN2 were significantly associated with ypT3-4 disease (65·7 and 83·0 per cent respectively versus 39·4 per cent for ypN0; P < 0·001). In unadjusted analyses, survival differed significantly between ypN groups (P < 0·001). Five-year survival rates were 81·6, 71·3 and 55·0 per cent for patients with ypN0, ypN1 and ypN2 disease respectively. After adjustment for confounding variables, ypN1 and ypN2 remained independently associated with overall survival: hazard ratio (HR) 1·61 (95 per cent c.i. 1·46 to 1·77) and 2·63 (2·34 to 2·95) respectively (P < 0·001). Overall survival was significantly longer in patients with ypN1-2 combined with ypT0-2 status than among those with ypT3-4 tumours even with ypN0 status (P = 0·031). Clinical nodal status before neoadjuvant therapy was not significantly associated with overall survival (HR 1·05, 0·97 to 1·13; P = 0·259).

Conclusion: Both ypT and ypN status is of prognostic significance following neoadjuvant therapy for rectal cancer.