Bariatric Surgery Cuts Risk for Obesity-Related Cancers: Study

For years evidence has pointed to multiple health benefits associated with bariatric surgery, including improvements in diabetes, sleep apnea, and blood pressure. Now researchers are adding cutting cancer risk by more than half to the list.

A retrospective, observational study of patients with obesity at 47 US healthcare organizations found that over 10 years, 4% who had bariatric surgery developed certain cancers compared with 8.9% of their peers who did not undergo such surgery.

"We did see a difference in breast cancer, colon cancer, liver cancer, and ovarian cancer incidence...with patients in the bariatric surgery group having lower incidence of these four types of cancers when compared to the nonsurgical control group," said Vibhu Chittajallu, MD, lead author and a gastroenterology fellow at Case Western Reserve University and University Hospitals in Cleveland, Ohio.

The obesity epidemic is "one of the most serious health challenges in the US today," Chittajallu added during an April 27 media briefing during which select research was previewed for Digestive Disease Week (DDW) 2023. Obesity has been associated with multiple serious illnesses, including type 2 diabetes, heart disease, and cancer.

Obesity is also common. The CDC reports that nearly 42% of American adults have obesity, and rates continue to rise.

Chittajallu and colleagues used billing codes in a national database to identify 55,789 patients with obesity who underwent bariatric surgery (sleeve gastrectomy, gastric bypass, or gastric band procedures) and a control group of the same size who did not have surgery.

Investigators controlled for risk factors that contribute to cancer development, including smoking history, alcohol use, heart disease, and hormone therapies.

Key Findings

In 10 years of follow-up, 2206 patients who underwent bariatric surgery developed an obesity-associated cancer compared with 4960 patients who did not have bariatric surgery.

The bariatric surgery group had lower numbers of new cases for six types of cancers (Table 1).

Table 1. New Cancer Cases Over 10 Years With vs Without Bariatric Surgery

Cancer Type	Cancer Cases, Bariatric Surgery, n	Cancer Cases, No Bariatric Surgery, n
Breast	501	751
Colon	201	360
Liver	969	2198
Pancreatic	54	86
Ovarian	130	214
Thyroid	154	175

The differences were significant in four cancer types associated with obesity: breast cancer (P = .001), colon cancer (P < .01), liver cancer (P < .01), and ovarian cancer (P = .002).

The incidence of several other cancers, including renal carcinoma, and rectal and endometrial cancers, was not significantly different between the groups.

The mechanisms underlying excess cancer cases in patients with obesity are not completely understood, Chittajallu said. Bariatric surgery has been shown to decrease excess inflammation, elevate insulin, and moderate hormone levels.

'Fascinating' Study But Questions Remain

The study is "fascinating," said Loren Laine, MD, moderator of the media briefing. "Obesity is clearly associated with a number of different cancers, and that's very important. So, it makes logical sense that if you lose weight, you will reduce that risk."

Although investigators controlled for several known cancer risk factors, there are some they couldn't control for because they were not included in the database, and there could be unknowns that also affected the results, noted Laine, who is professor of medicine (digestive diseases) and chief of digestive health at Yale University School of Medicine in New Haven, Connecticut.

"You have to be circumspect when you look at retrospective observational studies," he added.

It would be helpful to know when most cancers developed over the 10 years, Laine said. Chittajallu responded that the research team did not include cancers that developed in the first year after bariatric surgery to minimize incidental findings, but he did not provide a timeline for the cancers that developed.

Another unanswered question, Laine said, is whether a dose–response relationship exists. If future research shows that the more weight a person loses, the more likely they are to have a reduction in cancer risk, "that would be fascinating," he said. Also, it would be interesting to know if endoscopic interventions and weight-loss medications decrease cancer risks in people with obesity.

More research is needed to understand how bariatric surgery affects cancer risk, Chittajallu said. "But the significant findings from this study suggest it's an exciting avenue for further study."

DDW 2023 will be held May 6-9 in Chicago and virtually.

The study was independently supported. Chittajallu and Laine have reported no relevant financial relationships.

Digestive Disease Week (DDW) 2023. Abstract 443. To be presented May 7, 2023.

Damian McNamara is a staff journalist based in Miami. He covers a wide range of medical specialties, including infectious diseases, gastroenterology, and critical care. Follow Damian on Twitter: @MedReporter.

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