Does the location of colon cancer – left or right side – matter for survival? A new report published online by JAMA Oncology reviewed medical literature to examine the prognostic role of a primary colon cancer tumor being located on the left vs. right side.

It has been suggested that localization of colon cancer on either the right or left side may influence prognosis because of differing biological features. Clinical presentation for right and left colon cancer can differ and right and left colon cancers are also genetically distinct.

A review and meta-analysis by Fausto Petrelli, M.D., of the ASST Bergamo Ovest, Treviglio, Italy, and coauthors included 66 studies and more than 1.4 million patients with a median follow-up of 65 months.

Left-sided primary tumor location was associated with a nearly 20 percent reduced risk of death, according to the analysis. This difference was independent of many clinical factors like tumor stage and receipt of adjuvant chemotherapy.  The authors note a number of possible reasons for this apart from biological differences.

The authors note limitations to their study, which cannot establish causality.
"Based on the results of this study, the side of origin of colon cancer (left vs. right) should be acknowledged as a criterion for establishing prognosis in both earlier and advanced stages of disease. Moreover, primary tumor locations should be carefully considered when deciding treatment intensity in metastatic and locoregional settings, and should represent an important stratification factor for future adjuvant studies," the article concludes.

No conflict of interest disclosures were reported.