LAUSR

694Background: The impact of primary tumour sidedness has recently been demonstrated in patients with metastatic colorectal cancer (mCRC). Differences in right (R) versus left (L) sided mCRC may be due to differences in consensus molecular subtyping. Clinically predictive mutations in ras, (kras, nras and braf) may also help drive some of the differences in outcome. However, patients with mCRC who undergo surgical resection of CRLM often have a good prognosis. The aim of this study was to assess the impact of tumour sidedness on OS after resection of CRLM. Methods: Patients who underwent resection of CRLM in the province of Alberta, Canada were identified from 2004-2016. Tumour sidedness was determined by chart review, with R from the cecum to transverse and L from splenic flexure to sigmoid. Where available, ras mutational status was collected. OS was measured from the time of CRLM resection to death or last follow-up using the Kaplan-meier method. R and L were compared using the log-rank test and a Cox ...