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Are Differences in Mutation and Survival Associated With Sidedness of Colorectal Cancer?

By: Kayci Reyer
Posted: Tuesday, October 30, 2018

According to a retrospective review published in the Journal of Gastrointestinal Oncology, a difference in the prevalence of genetic mutations in left-sided versus right-sided colorectal cancers may help explain the discrepant outcomes and treatment responses between the two. BRAF and CTNNB1 mutations were found to be more prevalent in patients with right-sided colorectal tumors, who also had worse outcomes than those who had left-sided tumors.

“While genetic differences between right- and left-sided [colorectal cancer] have long been described, the genetic and molecular drivers underlying differences in prognosis and treatment response remain incompletely understood,” noted Christopher E. Jensen, MD, of the Hospital of the University of Pennsylvania, and colleagues.

At a single referral center, the researchers examined the frequency of mutations in 38 genes and the overall survival in left-sided (the descending colon to the rectum) and right-sided (the cecum to the splenic flexure) colorectal cancer. A total of 288 cases were analyzed in this study, including 167 left-sided, 103 right-sided, and 18 that were synchronous or without a clear primary side. From the date of diagnosis, patients with left-sided colorectal cancer had a longer overall survival (median 1,823 days vs. 1,006 days for right-sided cases, P = .004).

Of the 38 genes analyzed, BRAF and CTNNB1 mutations were found to be more common in patients with right-sided cases. A total of 15.5% of participants with right-sided colorectal cancer had a BRAF mutation, compared with 4.8% of those with left-sided cancers (P = .003). CTNNB1 mutations were found in 3.9% of participants with right-sided cases, compared with no instances occurring in those with left-sided primary tumors (P = .01).

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