Primary Colorectal Cancer Location May Influence Survival

The researchers used data from a prospective pharmacogenetic study and two randomized phase III trials. The primary end point was overall survival, with progression-free survival assessed according to tumor location, i.e., proximal or distal of the splenic flexure.

The results showed that over the three studies, about 70% of patients had left-sided primary tumors and had better survival outcomes than those with right-sided tumors. In one study, right-sided tumor location also had a negative prognostic value independent of BRAF mutation status or histological type. The researchers found that efficacy of bevacizumab was independent of tumor location, but right-sided tumors were associated with development of chemoresistance, hinting at biological differences. The study was published in the February 25, 2015, issue of JNCI: Journal of the National Cancer Institute.

“The two halves of the human colon have different embryonic origins and gene expression patterns, and these differences may also play a role in cancer biology,” concluded lead author Fotios Loupakis, MD, PhD, of the USC Norris Comprehensive Cancer Center, and colleagues. “Given the consistency across an exploratory set and two confirmatory phase III studies, side of tumor origin should be considered for stratification in randomized trials.”

Colorectal cancer is the development of cancer in the large intestine. Most deaths due to colon cancer are associated with mCRC (stage IV colorectal cancer). Cure is not possible for most patients with mCRC, although some patients who have limited involvement of distant organs (particularly restricted to the liver and/or lung) can be cured with surgery. For others, chemotherapy is the most appropriate option. Chemotherapy does not cure mCRC, but it can improve symptoms and prolong life.

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