N1c colon cancer and the use of adjuvant chemotherapy: a current audit of the National Cancer Database.

Abstract

Colorectal cancer staging has evolved to define N1c as the presence of tumour deposits without concurrent positive lymph nodes. Work to date reports poor prognosis in N1c colon cancer, with Stage III categorization and adjuvant chemotherapy (AC) recommended. No study has yet evaluated the prevalence, treatment compliance or treatment-related outcomes on a national scale. We aimed to evaluate the prevalence of N1c colon cancer, use, outcomes and factors associated with AC in the USA. The National Cancer Database was reviewed for N1cM0 colon adenocarcinomas that underwent resection from 2010 to 2016. Cases were stratified into 'AC' or 'no AC' cohorts. The Kaplan-Meier method was used to estimate overall survival (OS) and compare the AC and no AC cohorts using the log-rank test. Multivariable logistic regression identified factors associated with AC. The main outcome measures were the prevalence and factors associated with AC use and its impact in N1c disease. Of the 5684 (1.59% of 357752) colon adenocarcinomas that were N1c, 55% (n=3071) received AC. AC significantly improved 1-, 3- and 5-year OS compared with no AC (96.2%, 80%, 67.4% and 72.9%, 48.5%, 33.8%, respectively; P<0.001). Compared with the no AC group, AC patients were younger, had less comorbidity, were of the male gender and received minimally invasive surgery at an academic treatment centre (all P<0.05). Socioeconomic and procedural factors significantly impacted the use of AC. In the USA, AC is underutilized in N1c colon cancer despite significantly improved OS. Socioeconomic and procedural factors associated with AC were identified, highlighting disparities in AC use and opportunities to improve oncological outcomes and survival.