Primary tumor location impacts survival in colorectal cancer patients after resection of liver metastases

Background and Objectives: Right-sided colon cancers (R-CC) are associated with worse outcomes compared to left-sided colon cancers (L-CC). We hypothesize that R-CC with synchronous liver metastases who undergo resection of primary and metastatic sites have worse survival and that survival will vary significantly among R-CC, L-CC, and rectal cancer (ReC). Methods: The Surveillance, Epidemiology, and End Results (SEER) database from 2010 to 2016 was used to identify colorectal cancer patients with liver metastases who underwent surgical resection of both primary and metastatic disease. Survival was analyzed by multivariate Cox regression. Results: A total of 2275 patients were included; 38% R-CC, 46% L-CC, and 16% ReC. R-CC primary tumors tended to be larger than 5 cm, higher grade, and mucinous (all P <.001). Compared to patients with R-CC, both L-CC and ReC had improved overall (HR 0.72; P <.001; HR 0.75, P =.006) and disease-specific (HR 0.71, P <.001; HR 0.73, P =.008) survival. There was no difference in survival between L-CC and ReC. Conclusions: Patients with R-CC have significantly worse survival than L-CC or ReC. This provides additional evidence that R-CC tumors are fundamentally different from L-CC and ReC tumors. Future studies should determine factors responsible for this disparity, and identify targeted treatment based on primary tumor location.