Bariatric Surgery Cuts Cancer Incidence, Death Risk

Weight loss, even achieved through bariatric surgery, reduced the risk of obesity-related cancer, researchers reported.

In a study of over 30,000 adults with obesity, only 2.9% of those who opted for bariatric surgery were diagnosed with cancer during a 10-year follow-up versus 4.9% of nonsurgical controls (absolute risk difference 2.0%, 95% CI 1.2%-2.7%), according to Steven E. Nissen, MD, of the Cleveland Clinic, and colleagues.

This translated to an incidence rate of 3.0 events vs 4.6 events per 1,000 person-years, respectively, and a 32% reduced risk for developing obesity-related cancer following weight loss from bariatric surgery (adjusted HR 0.68, 95% CI 0.53-0.87, P=0.002).

Obesity-related cancer was a composite of these 13 cancer types: esophageal adenocarcinoma, renal cell carcinoma, postmenopausal breast cancer (diagnosed at ≥55 years of age) or breast cancer in younger patients who had bilateral oophorectomy, multiple myeloma, and cancers of the gastric cardia, colon, rectum, liver, gallbladder, pancreas, ovary, corpus uteri, and thyroid.

Findings from the Surgical Procedures and Long-term Effectiveness in Neoplastic Disease Incidence and Death (SPLENDID) study were presented at the American Diabetes Association (ADA) annual meeting and published in JAMA.

"Patients can lose 20 to 40% of their body weight after surgery, and weight loss can be sustained over decades. The striking findings of this study indicate that the greater the weight loss, the lower the risk of cancer," said co-author Ali Aminian, MD, also of the Cleveland Clinic, in a statement.

The risk of all types of cancer was also significantly lower for patients who underwent bariatric surgery (HR 0.83, 95% CI 0.69-0.99, P=0.04).

Nissen's group included patients who underwent the two most common bariatric procedures today: Roux-en-Y gastric bypass and sleeve gastrectomy. Compared with nonsurgical obesity care, both procedures were tied to a lower risk for cancer and there was no significant difference between the two types of procedures:

• Roux-en-Y: aHR 0.70 (95% CI 0.53-0.92)

• Sleeve gastrectomy: aHR 0.66 (95% CI 0.44-1.00)

The benefits of bariatric surgery also extended to cancer-related mortality. Only 21 patients who underwent bariatric surgery died due to cancer compared with 205 patients in the nonsurgical group (incidence rate of 0.6 events vs 1.2 events, respectively, per 1,000 person-years).

During the decade-long follow-up, this translated to a cumulative incidence of cancer-related mortality of 0.8% in the bariatric surgery group versus 1.4% in the nonsurgical control group.

Overall, bariatric surgery was tied to a 48% reduced risk for cancer-related death (adjusted HR 0.52, 95% CI 0.31-0.88, P=0.01).

As for specific cancers, the most common cancers seen among these patients included female breast cancer and endometrial cancer. Compared with nonsurgical controls, bariatric surgery was tied to a 53% reduced risk for incident endometrial cancer (aHR 0.47, 95% CI 0.27-0.83).

"According to the American Cancer Society, obesity is second only to tobacco as a preventable cause of cancer in the United States," Nissen pointed out in a statement. "This study provides the best possible evidence on the value of intentional weight loss to reduce cancer risk and mortality."

While this isn't the first study to demonstrate the protective benefits of bariatric surgery, "it does lend even more support to the finding that people who undergo bariatric surgery may experience a decreased risk of cancer," wrote Anita P. Courcoulas, MD, MPH, of the University of Pittsburgh Medical Center, in an accompanying editorial.

A total of 30,318 patients were included with median ages and BMIs of 46 and 45, respectively. The majority of the cohort were white, and as to be expected, 77% were female. Among the 5,053 patients who opted for bariatric surgery, 66% underwent Roux-en-Y gastric bypass and 34% underwent sleeve gastrectomy.

At the 10-year mark, patients who underwent bariatric surgery lost 60.6 lb (27.5 kg), while nonsurgical controls only lost an average of 6 lb (2.7 kg).

"Currently, bariatric surgery is the only available treatment that can provide this magnitude and durability of weight loss," the researchers noted. They referenced the Look AHEAD study, which found that weight loss from intensive lifestyle intervention didn't yield enough weight loss to significantly reduce the risk of obesity-related cancer or mortality.

Courcoulas noted that additional research is still needed on this topic, potentially warranting a randomized clinical trial. She suggested "it may be more practical to consider such randomized clinical trials among patients at high risk for specific types of cancer, such as women at risk for endometrial cancer or breast cancer."