The Lymph Node Ratio Optimizes Staging System while Adjuvant Chemotherapy Plays an Invalid Role for Patients with Nonmetastatic Colorectal Neuroendocrine Carcinomas: A Propensity Score Matching Analysis of Patients from the Surveillance, Epidemiology, and End-Results Database

Abstract

Objective: Colorectal neuroendocrine carcinoma (CRNEC) is rare and little is known about survival benefit between lymph node ratio (LNR) and improved overall survival (OS), and so is the adjuvant chemotherapy (AC). We aim to evaluate the survival benefit of LNR and AC in patients with nonmetastatic CRNEC following resection. Methods: Patients with resected nonmetastatic CRNECs were identified in Surveillance, Epidemiology, and End Results (SEER) during year 1992 to 2016. A Log-rank test was conducted to determine the survival difference. The survival benefit was evaluated using a competing-risks regression model and propensity score-matched (PSM) techniques were used to reduce the selection bias.Results: A total of 251 patients met the inclusion criteria, of which, 152 patients (60.56%) received AC. The age of 60 (P=0.848) and number of 12 of resected regional lymph nodes (P=0.082) acted as an optimal cutoff value in terms of survival, failing to reach a significance. Chemotherapy failed to bring survival benefit (hazard ratio [HR], 0.959; 95% confidence interval [CI], 0.649-1.416; P=0.832). Current N classification was not a significant predictor of patient survival (N1: P = 0.174; N2: P=0.028, compared to N0, respectively). Multivariate analyses explored the revised Nr classification, based on LNR of 0.30 and 0.75 as cutoff value (Nr0: LNR£0.30; Nr1: 0.3<LNR£0.75; Nr2: LNR >0.75), as an independent prognostic factor (Nr1: P = 0. 003; Nr2: P<0.001, compared to Nr0, respectively). With the foundation of revised Nr classification, a revised TNrM was proposed for nonmetastatic CRNEC: stage I (T1–2Nr0), stage II (T1-2Nr1 or T3Nr0–1 or T4Nr0), and stage III (TxNr2 or T4Nr1). TNrM stage had better stratification according to Kaplan-Meier survival curves (P <0.001). Conclusions: AC seems invalid for improving the survival of patients with nonmetastatic CRNECs following resection. The LNR more accurately predict survival of CRNEC patients than current N classification.