In a new study, researchers found that obesity increases the risk of colon cancer, but weight-loss surgery may bring the risk back to normal.
They found people who are obese have a 34% higher risk of colon cancer than the general population, but any type of bariatric (weight-loss) surgery can bring their risk back in line.
They suggested that people aged 50 to 75 are particularly concerned by the risk of developing colorectal cancer and all of them should undergo a screening test regularly.
The research was conducted by a team at the Centre Hospitalier Universitaire de Nice.
The aim of weight-loss surgery is to create a smaller stomach so patients feel full faster and eat less.
In gastric banding, a silicone band is placed around the top of the stomach to make it smaller.
With gastric bypass, the stomach is stapled smaller and the small intestine is connected to it. In a sleeve gastrectomy, about 80% of the stomach is removed.
In the study, the researchers reviewed data collected between 2009 and 2018 on more than 1 million people with obesity aged 50 to 75.
Over five years of follow-up, more than 13,000 developed colon or rectal cancer.
Among those who had weight-loss surgery, the colorectal cancer rate was 0.6%. For those who didn’t have surgery, it was 1.3%.
The team found that fewer cases of colon and rectal cancer were diagnosed after gastric bypass and sleeve gastrectomy procedures than after adjustable gastric banding.
More noncancerous polyps were found after gastric banding than after gastric bypass or sleeve gastrectomy, the researchers reported.
The team says weight-loss surgery improves how much insulin the body makes, which is why many patients’ diabetes goes away after surgery, and that could be the reason for the decreased colon cancer risk.
Insulin resistance and metabolic syndrome and obesity are linked to colon cancer, and people have talked about using the diabetes drug metformin for colon cancer.
The team says the risk of colon cancer likely rises if patients regain their weight. But people can buy five to 10 years of life by lowering the risk.
Losing weight may also reduce the risk of other cancers linked to obesity, including uterine cancer and post-menopausal breast cancer.
The lead author of the study is Dr. Laurent Bailly of the Centre Hospitalier Universitaire de Nice.
The study is published in JAMA Surgery.
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