Prognostic value of N1c in colorectal cancer: a large population-based study using propensity score matching.

ABSTRACT

PURPOSE: We conducted this large population-based study to investigate the prognostic significance of N1c. METHODS: Patients diagnosed with colorectal cancer from the surveillance, epidemiology, and end results (SEER) database between January 1, 2010, and December 31, 2010, were included in the sample. The primary outcome of interest used in our study was cause-specific survival (CSS). Cox proportional hazards models and Kaplan-Meier methods were used to evaluate the prognostic value of N1c. Propensity score matching (PSM) was implemented to reduce the possibility of selection bias using a logistic regression model. RESULTS: A total of 19,991 patients diagnosed with colorectal cancer were identified from the SEER database. The median follow-up time of the whole cohort was 60 months (0-71 months). Multivariate Cox analysis showed that N1c was associated with significantly higher risk of colorectal cancer-specific mortality compared with N0 (HR = 1.962, 95%CI = 1.642 to 2.343, P < 0.001) and N1a (HR = 0.818, 95%CI = 0.678 to 0.987, P = 0.036); N1c was associated with significantly lower risk of colorectal cancer-specific mortality compared with N2a (HR = 1.296, 95%CI = 1.081 to 1.554, P = 0.005) and N2b (HR = 1.663, 95%CI = 1.391 to 1.989, P < 0.001). Yet the CSS difference between N1b and N1c did not achieve statistical difference (HR = 1.089, 95%CI = 0.909 to 1.304, P = 0.354). CONCLUSIONS: The large population-based and propensity score-matched study with long follow-up time provides the first evidence that CSS difference between N1b and N1c does not achieve a statistical difference.