The incidence of newly diagnosed cancer was nearly cut in half in individuals with obesity who underwent bariatric surgery compared to matched controls who did not, according to Vibhu Chittajallu, MD, a gastroenterology fellow at Case Western Reserve University and University Hospitals. Dr. Chittajallu is presenting the results of this multi-center population-based study at Digestive Disease Week® (DDW) 2023.

“There is a lot of strong data on the benefits of weight loss after bariatric surgery,” said Dr. Chittajallu, “but its impact on cancer hasn’t been fully investigated. This study further highlights the role of bariatric surgery and its association with de novo cancer formation.”

The study retrospectively analyzed the records of more than 55,700 patients with obesity (body mass index >35) from 47 health care organizations across the U.S. who underwent bariatric surgery and compared them to a nonsurgical control group. The study included patients who had undergone sleeve gastrectomy, gastric bypass or gastric band, and controlled for multiple risk factors, including smoking, alcohol use and other comorbidities.

Researchers focused on the occurrence of de novo obesity-related cancers starting one year after the index date, i.e., bariatric surgery in the surgery group and obesity diagnosis in the control group. Patients were followed up between 12 months and 10 years. Key findings include:

• Bariatric surgery reduced the rate of de novo cancer diagnosis by half. At ten years following the index date, the cumulative incidence of obesity-related cancers was 4% in the surgery group and 8.9% in the nonsurgery group (p<0.001).
• Lower prevalence rates were consistently lower for nearly all obesity-related cancers. The prevalence of breast cancer (0.9% vs 1.3%), colon cancer (0.4% vs 0.6%), liver cancer (1.7% vs 3.9%), and ovarian cancer (0.2% vs 0.4%) was statistically lower in the surgery group compared to the nonsurgery group.

A key advantage of this study is its sample size. While smaller studies have investigated an association between bariatric surgery and cancer, none have been as large as this.

“Using large national databases, we were able to observe trends that haven’t been accessible in smaller studies,” Dr. Chittajallu said. “For example, this allowed us to better pinpoint the impact of bariatric surgery on specific cancer types.”

Dr. Chittajallu cautioned that, due to its retrospective nature, it is difficult to draw too many conclusions about the cause-and-effect relationship between bariatric surgery and cancer risk, but is excited at the types of questions and hypotheses this work generates. For example, he is interested in investigating whether the type of bariatric surgery a patient undergoes has a differential impact on cancer incidence and whether nonsurgical weight loss modalities may have a similar protective effect.

“People often consider the primary benefit of bariatric surgery to be weight loss and the physical and psychological benefits that come with that,” said Dr. Chittajallu. “We’re continuing to build evidence on how significant this weight loss can be to overall health, including cancer risk.”

Dr. Chittajallu’s presentation, “Bariatric surgery decreases the risk of developing cancer: a multicenter population-based study,” abstract 443, on Sunday, May 7, at 11:14 a.m. CDT, is part of the session “SSAT Presidential Plenary II.”