LAUSR

Many biological differences exist between the right-side colon and the left-side colon, including differing embryologic origins, distinct site-associated microbiota, and differential gene expression and methylation. Recent studies have reported a prognostic value for primary tumor sidedness. Several randomized trials have assessed the prognostic influence of primary tumor location in patients with unresectable colorectal cancer treated with moleculartargeted agents (e.g. vascular endothelial growth factortargeted antibody [bevacizumab] and epidermal growth factor receptor-targeted antibodies [cetuximab, panitumumab]), and pooled analyses have revealed a significantly poorer prognosis in patients with right-sided tumors than those with left-sided tumors. However, questions remain regarding the prognostic value of tumor sidedness with respect to treatment strategy, use of targeted agents, and palliative resection of the primary tumor. The aim of the present study was to evaluate the prognostic value of tumor sidedness, specifically with respect to overall survival (OS), in patients with unresectable stage IV colorectal cancer regardless of treatment strategy. PRESENT