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Bariatric Surgery can lower obesity-related cancer

Among adults with obesity, those who lost weight intentionally with bariatric surgery had significantly less obesity-related cancer and cancer-related mortality than those who did not have surgery.


“Bariatric surgery is the most effective currently available treatment for obesity. Patients typically lose 20% to 35% of body weight after surgery, which is often sustained for many years,” Ali Aminian, MD, an academic surgeon in the department of general surgery at the Bariatric and Metabolic Institute at Cleveland Clinic, Cleveland, and colleagues wrote. “A few observational studies have reported an association between bariatric surgery and reduced cancer risk.”

The SPLENDID matched cohort study enrolled 30,318 adults (median age, 46 years; 77% women), of whom 5,053 had a BMI of 35 kg/m2 or greater and underwent bariatric surgery at a U.S. health system between 2004 and 2017. These patients were matched with 25,265 patients with obesity who did not undergo bariatric surgery.

The primary outcome was time to incident obesity-associated cancer and cancer-related mortality.

After a median follow-up period of 6.1 years, the mean between-group difference in body weight at 10 years was 24.8 kg for a 19.2% greater weight loss among the patients who had bariatric surgery. During follow-up, 96 patients who underwent bariatric surgery and 780 nonsurgical patients had an incident obesity-related cancer event (3 vs. 4.6 events per 1,000 person-years).
At 10 years, the cumulative incidence of obesity-associated cancer was 2.9% among patients who underwent bariatric surgery and 4.9% among nonsurgical patients (adjusted HR = 0.68; 95% CI, 0.53-0.87; P = .002).

Overall, 21 surgery patients and 205 nonsurgical patients experienced cancer-related mortality (0.6 vs. 1.2 events per 1,000 person-years). At 10 years, the cumulative incidence of cancer-related mortality was 0.8% among the surgery group and 1.4% among the nonsurgical patients (aHR = 0.52; 95% CI, 0.31-0.88; P = .01).

In an accompanying editorial, Anita P. Courcoulas, MD, MPH, surgeon in the department of surgery at the University of Pittsburgh Medical Center, noted that although this study demonstrated important associations between bariatric surgery and lower incidence of cancer and cancer-related mortality, more research is required to address the important issues to advance future work in this area.

“More work needs to be done through large, well-designed studies that would include data on cancer screening, data from tumor registries, more detailed individual patient data and investigations of the basic mechanisms of effect,” Courcoulas wrote. “If this association is further validated, it would extend the benefits of bariatric surgery to another important area of long-term health and prevention.”


Emily J. Gallagher, MD, PhD

In 2016, the International Agency for Research on Cancer reported that obesity was associated with an increased risk for 13 cancer types. Individuals with obesity also have a greater risk for cancer mortality. Despite these associations, it is unclear if intentional weight loss mitigates these excess risks. Previous observational studies reported that individuals who underwent bariatric surgery had a reduced risk for developing cancer, but questions remain regarding the potential benefits of specific surgical procedures on cancer risk and long-term cancer mortality.

The Surgical Procedures and Long-term Effectiveness in Neoplastic Disease Incidence and Death (SPLENDID) study evaluated the risk for developing one of the 13 obesity-associated cancer types, as well as the risk for any cancer and cancer-related mortality in the bariatric surgery group (n = 5,053) compared with matched individuals who did not undergo bariatric surgery (n = 25,265), with a median age of 46 years.

During a median follow up of 6 years, the bariatric surgery group lost almost 25 kg more weight than the non-surgery group. They had a 32% decreased risk for developing one of the 13 obesity-associated cancers, and a 17% reduced risk for developing any cancer. Cancer mortality was almost 50% lower in the bariatric surgery group compared with the non-surgery group. The degree of weight loss after bariatric surgery progressively reduced cancer risk in a dose-dependent manner. A greater effect was seen in females than males; however, 77% of the cohort was female. Bariatric surgery appeared to equally benefit Black and white individuals and those who were or were not taking diabetes medications.

A number of questions remain to be determined, for example: What are the mechanisms behind the reduction in cancer risk? Could newer medications that produce substantial weight loss have similar effects? As a small minority of people with obesity undergo bariatric surgery, understanding the mechanisms through which bariatric surgery reduces obesity-associated cancer risk and mortality is important to develop strategies to mitigate the risk for the broader population.

Emily J. Gallagher, MD, PhD
Assistant Professor of Diabetes, Endocrinology and Bone Diseases
Director of the ABIM Research Pathway
Associate Program Director, Internal Medicine Residency Program
Icahn School of Medicine at Mount Sinai
Disclosures: Gallagher reports consulting/advisory roles for Novartis, Seattle Genetics and SynDevRx.