Weight-loss surgery cuts risk of developing colorectal cancer by more than a third

People who had weight-loss surgery were 37% less likely to develop colorectal cancer compared to individuals with obesity who did not have the surgery, according to a new study presented here today at the American Society for Metabolic and Bariatric Surgery (ASMBS) Annual Meeting (#ASMBS2022).

The American Cancer Society estimates that this year more than 150,000 people will be diagnosed with colorectal cancer, the third leading cause of cancer-related deaths in the United States. Having obesity or overweight increases the risk for many types of cancer including colorectal cancer, as well as other life threatening diseases and conditions including type 2 diabetes, heart disease and stroke.

In a meta-analysis, researchers from the Military Institution of Aviation Medicine in Warsaw, Poland, Texas Tech School of Medicine in El Paso and the Mayo Clinic College of Medicine in Rochester, MN examined data from 13 previous studies on weight-loss surgery and colorectal cancer that followed more than 3.2 million patients for up to 10 years. The included studies were published between 2008 and 2021, which researchers say covers a longer and more up-to-date period than previous systematic reviews on the subject.

"Bariatric surgery may offer significant protection against colorectal cancer in individuals with obesity that extends at least 10 years, the length of follow-up in several of the studies we analyzed," said study co-author Michal Janik, MD, a general and bariatric surgeon at the Military Institution of Aviation Medicine. "This is an important finding because colorectal cancer takes time to develop and even over decade the protective effect is still there."

The study did not account for risk factors other than obesity and did not measure weight loss or correlate findings to any particular method of weight-loss surgery. Researchers say future studies should take into account the difference in the incidence of colorectal cancer among the different types of bariatric surgery and in patients with different durations of obesity.

"This study shows that when you treat obesity with weight-loss surgery, you may also be preventing colorectal cancer at the same time, not to mention a whole host of other diseases and conditions that are improved, resolved or prevented," said Shanu Kothari, MD, President, ASMBS, who was not involved in the study.