139 Background: Differences in embryological origin and tumor biology distinguish right-sided colon cancer (RCC) from left-sided colon cancer (LCC). Previous studies characterizing the prognostic impact of colon cancer laterality on clinical outcomes in non-metastatic colon cancer have been conflicting, thus closer examination is needed. Methods: Using the NCDB, patients with stage I-III colon cancer between 2004-2014 were stratified according to tumor location; RCC vs. LCC. Patient (pt) and tumor characteristics were compared in univariate analysis, survival (OS) was estimated by Kaplan-Meier (KM) curves and Cox proportional hazards modeling. Binomial logistic regression analysis was utilized to identify variables associated with colon cancer laterality. Results: Of the 342,735 pts who met inclusion criteria, 210,343 (61.4%) were diagnosed with RCC, and 132,392 (38.6%) with LCC. Pts with RCC were older (mean 71.6 vs. 66.4 years, p< 0.001) and predominantly female (65% vs. 35%, p< 0.001) compared to those with LCC. A trend towards poorer OS was seen in pts with RCC (mean 91.0 mos [95% CI: 90.2-91.8]) compared to LCC (112.2 mos [95% CI: 110.9-113.6]) in unadjusted analysis. On Cox multivariable adjusted analyses there was a significant but minimal impact on OS and laterality (hazard ratio or HR [LCC as ref] 0.978, 95% CI 0.967-0.989 p< 0.0001). Multiple unadjusted KM survival analyses showed RCC with T4 disease, high-grade, LVI/PNI, positive margins, N0-N2 disease, tumor deposits, and receipt of adjuvant chemotherapy had poorer OS than those features in LCC (all p < 0.0001). Binomial logistic regression showed RCCs were significantly more likely to be higher grade (odds ratio or OR 2.024) and MSI-H (OR 2.010) with trends (nonsignificant) towards more likely having N1-2 positive disease, LVI, less receipt of adjuvant chemotherapy, and fewer tumor deposits. Conclusions: The impact of sidedness on prognosis in stage I-III colon cancer is complex. In this large, population-based study, RCC tends to be associated with more adverse prognostic features than LCC. More investigation into the biologic differences between RCC and LCC is warranted and how they impact phenotype and survival.
941 – The Impact of Kras Mutation on the Presentation and Prognosis of Non-Metastatic Colon Cancer: An Analysis from the National Cancer Database
