Aspirin lowers bowel cancer risk in obese people with inherited cancer syndrome
The new analysis of the CAPP2 trial showed that obesity heightened the risk of bowel cancer among people with the condition, who already have a much higher risk of bowel and other cancers than the general population.
"This information is helpful for advising people with an inherited risk of bowel cancer" - Professor Matthew Seymour, Cancer Research UK
However, the effect was observed most clearly in people with a body mass index (BMI) over 30, and in men.
The effect also seemed to differ depending on the precise genetic cause of Lynch syndrome, which is caused by inherited faults in one of four genes, all of which are involved in repairing damaged DNA.
Obesity increased the risk for people with faults in a gene called MLH1, yet the same effect was not seen in those carrying with errors in a different gene, MSH2.
The findings, published in the Journal of Clinical Oncology, also suggest that this increased risk in overweight and obese people can be reduced by regular aspirin.
According to Professor Matthew Seymour, a bowel cancer expert at Cancer Research UK - which helped fund the study - the discovery built on previous analysis from the trial.
"CAPP2 has already produced valuable information, showing that for people with an inherited tendency to develop bowel cancer, their risk can be reduced by taking aspirin.
“Now this additional analysis from the same clinical trial shows that avoiding becoming obese may be especially important for people with this inherited condition."
The researchers, based at Newcastle University and the University of Leeds, gave 937 patients with Lynch Syndrome either 600mg aspirin, or a placebo, every day for an average of two years.
After an average of nearly five years, 55 of them had developed bowel cancer.
Those taking placebos were almost three (2.75) times more likely to develop bowel cancer during this period, while those who were overweight or obese in the aspirin group had the same risk as those who had a normal weight.
"This information is helpful for advising people with an inherited risk of bowel cancer," siad Seymour.
"But it’s also important as it gives new clues about the mechanisms which may underly the rising incidence of bowel cancer in the general population, and provides important new leads for scientists working to understanding what triggers this disease and how to combat it,” he added.
Newcastle University’s Professor John Mathers, who led part of the study, said: “For those with Lynch Syndrome, we found that every unit of BMI above what is considered healthy increased the risk of bowel cancer by 7 per cent. What is surprising is that, even in people with a genetic predisposition for cancer, obesity is also a driver of the disease.”
However, Mathers remarked that, while weight loss could be important, for many Lynch Syndrome patients this can be difficult, so aspirin treatment may be a better option.
- Movahedi M 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) DOI: 10.1200/JCO.2014.58.9952