Bariatric Surgery Can Lead to Diabetes Remission, Cut Cancer Risk

Patients with obesity and type 2 diabetes who underwent bariatric surgery and had 10-year durable diabetes remission had a 60% lower risk of incident cancer than patients who had usual obesity care.

And women who had bariatric surgery had a 42% lower risk of having cancer during a median 21-year follow-up, compared to women who had usual obesity care.

These findings from 701 patients in the Swedish Obese Subjects (SOS) Study who had type 2 diabetes were recently published in Diabetes Care.

The results illustrate the “connection between glucose control and cancer prevention” and suggest that “among patients with type 2 diabetes, many cancer cases are preventable,” lead author Kajsa Sjöholm, PhD, associate professor of molecular medicine at Sahlgrenska Academy, University of Gothenburg, Sweden, said in a press release from the university.

“The global epidemic of both obesity and diabetes leads to an increased risk of cancer, as well as an increased risk of premature death,” added senior author Magdalena Taube, PhD, associate professor of molecular medicine in the same academy.

“It has been estimated that, over the next 10 to 15 years, obesity may cause more cancer cases than smoking in several countries,” she noted. Therefore, “strategies are needed to prevent this development, and our results can provide vital guidance for prevention of cancer in patients with obesity and type 2 diabetes.”

Durable Diabetes Remission Seems Key

Two thirds of the patients in the bariatric surgery group had vertical banded gastroplasty (65%), and the rest had adjustable or nonadjustable gastric banding (18%) or gastric bypass (17%).

Each type of bariatric surgery was associated with higher diabetes remission rates compared with usual care, in a previous study by these researchers, Taube told Medscape Medical News in an email

“In our present study,” she added, “we observed a non-significant trend, where patients with obesity and type 2 diabetes in the highest weight loss tertile (average weight loss -44.8 kg) had somewhat lower risk of cancer compared to the lowest tertile (average weight loss -14.9 kg).”

This might suggest, Taube continued, that with respect to cancer risk, surgery techniques resulting in greater weight loss (eg, Roux-en-Y gastric bypass and sleeve gastrectomy) should be recommended in patients with obesity and diabetes.

“However, it should also be noted that long-term diabetes remission seems imperative for cancer risk reduction,” she said, “and in a recent meta-analysis by McTigue et al published in JAMA Surgery 2020 it was shown that patients who had Roux-en-Y gastric bypass had greater weight loss, a slightly higher type 2 diabetes remission rate, less type 2 diabetes relapse, and better long-term glycemic control compared with those who had sleeve gastrectomy.”  

“The observed cancer reduction in women with obesity and type 2 diabetes is in line with previous findings showing that cancer risk reduction following bariatric surgery in patients with obesity is more marked among women than men,” Taube noted. This may be because cancer rates are higher in women with diabetes than in men with diabetes, and common cancer types associated with obesity are female-specific, she suggested.

The main cancers in women were breast cancer, followed by endometrial and colorectal cancer. In men, the main cancers were colorectal, prostate and urothelial/malignant skin cancer.  

Study Design and Findings

It is well established that obesity is a risk factor for 13 types of cancer, and some of these cancers (liver, pancreatic, endometrial, colon and rectal, breast, and bladder) may be related to type 2 diabetes. And bariatric surgery has been shown to reduce cancer risk in patients with obesity.

However, it is not clear how bariatric surgery may affect cancer risk in patients with obesity and type 2 diabetes.

To study this, the researchers examined data from 393 patients who underwent bariatric surgery and 308 patients who received usual obesity treatment, who were part of the SOS study.

The SOS study enrolled men with a body mass index (BMI) ≥ 34 kg/m2, and women with a BMI ≥ 38 kg/m2 who were 37 to 60 years old, between 1987 to 2001.

The current study outcome — cancer incidence in patients with obesity and type 2 diabetes — was not a prespecified outcome

The intervention groups were matched on 18 variables, including age, sex, serum insulin, alcohol, education, and smoking.

At baseline, the patients had a mean age of about 49 and 60% were women. They had a mean BMI of about 42 kg/m2 and a mean A1c of 7.8%.

On average, patients in the surgery group had lost 27.5 kg and 22.7 kg, and patients in the usual care group had lost 3.2 kg and 4.8 kg, at 2 years and 10 years, respectively.

During a median follow-up of 21 years, there were 74 incident cancers in the control group and 68 cancers in the bariatric surgery group.

The risk of cancer during follow-up was 37% lower in the surgery group than in the usual care group, after multivariable adjustment (adjusted hazard ratio, [HR] 0.63; 95% CI 0.44 – 0.89; P = .008).

A deeper dive showed that there were 86 incident cancers in women and 56 cancers in men. The risk of cancer was significantly lower in women who had bariatric surgery compared to those who had usual care (adjusted HR, 0.58; 95% CI 0.38 – 0.90, P = .016). However, the risk of cancer was not significantly lower in men who had bariatric surgery versus those who had usual care (adjusted HR 0.79, 95% CI, 0.46 – 1.38; P = .413).

Diabetes remission at 10 years was associated with a 60% reduced cancer incidence (adjusted HR, 0.40; 95% CI, 0.22 – 0.74, P = .003).

The study was funded by the Swedish state (under an agreement between the Swedish government and the county councils), the Swedish Research Council, the Novo Nordisk Foundation, the Swedish Heart-Lung Foundation, and the Swedish Diabetes Foundation. One author has received consulting fees from Johnson & Johnson. The other authors have no relevant financial disclosures.  

Diabetes Care. Published online November 19, 2021. Article

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