Obesity is associated with a significantly increased risk of colorectal cancer in patients with Lynch syndrome. However, regular aspirin use may lower that risk, according to a recent study published online ahead of print in the Journal of Clinical Oncology.

Researchers led by Mohammad Movahedi, MD, PhD, of the Beheshti University of Medical Sciences in Iran recruited 937 patients with Lynch syndrome to the CAPP2 study where they were randomly assigned to either aspirin (600 mg daily) or aspirin placebo, as well as resistant starch (30 g daily) or starch placebo.

They wanted to determine the link between increased adiposity and risk of colorectal cancer in patients with Lynch syndrome.

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At a mean follow-up of 55.7 months, the researchers found that 55 of the patients developed colorectal cancer. Colorectal cancer risk was 2.41 times greater in obese participants when compared with the reference group of underweight and normal-weight participants. Risk of colorectal cancer was increased by 7% for each 1 kg/m2 increase in body mass index.

In addition, risk of all Lynch syndrome-related cancers in obese participants was 1.77 times greater than the reference group. Upon subgroup analysis, obesity was associated with a 3.72 times greater risk of colorectal cancer in those patients with MLH1 mutation, but no excess risk was found in MSH2 or MSH6 mutations.

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However, the obesity-related excess risk of colorectal cancer was found to be exclusive to patients who were assigned to the aspirin placebo group.

“Obesity is associated with substantially increased colorectal cancer risk in patients with Lynch syndrome, but this risk is abrogated in those taking aspirin,” the authors concluded.


  1. Movahedi M, Bishop DT, Macrae F, et al. Obesity, aspirin, and risk of colorectal cancer in carriers of hereditary colorectal cancer: a prospective investigation in the CAPP2 study. J Clin Oncol.2015. [epub ahead of print]. doi: 10.1200/JCO.2014.58.9952.