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 with 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 10-15 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, Dr. Taube said in an interview.
“In our present study,” she added, “we observed a nonsignificant 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, Dr. Taube continued, that with respect to cancer risk, surgery techniques resulting in greater weight loss (for example, 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, 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,” Dr. 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.
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.