Clinicoepidemiological Study and Survival Analysis of Right versus Left Sided Colon Cancer Patients

Abstract

During the past decades an increased interest has been demonstrated concerning the distribution of colorectal cancer through the different segments of the colon. A trend toward an increasing percentage of right-sided cancer has been reported (Benedix et al., 2010). The data show that patients whose primary tumors originate on the left side of the colon (the descending colon, sigmoid colon, and rectum) survive significantly longer than those whose tumors originate on the right side (the cecum and ascending colon). Even in KRAS-Mutated Tumors, Left-Sided Tumors Are Associated With Improved Survival (ASCO, 2016). Venook et al. recently investigated the potential effect of primary tumor location on the clinical efficacy of patients treated on CALGB/SWOG 80405, and these findings were reported at the 2016 ASCO Annual Meeting. In a careful chart review, they determined that 68% of the primary tumors came from the left side of the colon or rectum and 27% of the tumors came from the right side. When OS was determined by sidedness of the primary tumor, there was an improvement in OS for patients with left-sided tumors compared with right-sided tumors (33.3 vs. 19.4 months, respectively), which was highly significant (p < .0001). For patients treated with bevacizumab, the improvement in OS was maintained in patients with left-sided tumors compared with right-sided tumors, albeit still higher for left-sided primary tumors (31.4 vs. 24.2 months, respectively) (Atreya, Yaeger and Chu, 2017).