Studies: Bariatric Surgery Best for Obese Diabetics

Bariatric surgery improves glycemic control better than optimal medical therapy alone for obese patients with type 2 diabetes, two randomized trials determined.

Hemoglobin A1c levels normalized to under 6% by 1 year for 42% of patients who got gastric bypass surgery and 37% who got sleeve gastrectomy compared with 12% on intensive medical therapy alone (P=0.002 and P=0.008), Philip R. Schauer, MD, of the Cleveland Clinic, and colleagues reported in the STAMPEDE trial.

After 2 years in a second trial, diabetes went into remission with fasting glucose under 100 mg/dL and A1c under 6.5% off medication in 75% of gastric bypass patients and 95% of biliopancreatic diversion patients compared with none on conventional medical therapy.

Metabolic control also improved more in the surgery groups of both trials, appearing online in theNew England Journal of Medicine.

“Although type 2 diabetes has been the domain of physicians, surgeons may now be able to claim greater success in achieving improved metabolic control,” an accompanying editorial suggested, calling the results likely practice changing.

Longer term and larger studies are needed to prove a durable benefit and whether the results would be as good in routine practice, noted editorialists Paul Zimmet, MD, PhD, of the Baker IDI Heart and Diabetes Institute, Melbourne, Australia, and K. George M.M. Alberti, DPhil, of King’s College Hospital in London.

“Meanwhile, the success of various types of bariatric surgery suggests that they should not be seen as a last resort,” they wrote. “Such procedures might well be considered earlier in the treatment of obese patients with type 2 diabetes.”

American Experience

The STAMPEDE (Surgical Treatment and Medications Potentially Eradicate Diabetes Efficiently) trial was presented at the American College of Cardiology meeting in Chicago in conjunction withNEJM publication.

It included 150 obese patients with a body mass index of 27 to 43 kg/m² (mean 36, 34% under 35 kg/m²) and uncontrolled diabetes with a hemoglobin A1c over 7.0% (mean 9.2%) randomized to Roux-en-Y surgery or sleeve gastrectomy or medical therapy alone.

All patients got intensive medical therapy according to American Diabetes Association guidelines with lifestyle counseling, weight management (recommended to include Weight Watchers), and newer diabetes drugs, such as the incretin analogues.

Glycosylated hemoglobin levels fell rapidly in the first 3 months after surgery. By 1 year, they reached a mean 6.4% after gastric bypass and 6.6% after sleeve gastrectomy compared with 7.5% with medical therapy alone (P<0.001 and P=0.003).

For the primary endpoint of a glycosylated hemoglobin under 6.0% at 1 year, the two bariatric surgery groups came up equal (P=0.59), though all who achieved that target in the gastric bypass group did so off diabetes medications versus 28% in the sleeve gastrectomy group.

Not surprisingly, weight loss after gastric bypass and sleeve gastrectomy exceeded that of medical therapy alone over 1 year (-64.8 and -55.3 lb versus -11.9 lb, both P<0.001).

Gastric bypass cut weight as well as BMI significantly more than sleeve gastrectomy (P=0.02 and 0.03, respectively).

“Reductions in the use of diabetes medications occurred before achievement of maximal weight loss, which supports the concept that the mechanisms of improvement in diabetes involve physiologic effects in addition to weight loss, probably related to alterations in gut hormones,” Shauer’s group noted.

Medication use to control glucose, lipids, and blood pressure fell significantly after both surgeries but increased with medical therapy alone.

Metabolic syndrome and insulin resistance also improved more with the bariatric procedures.

No patients died or had a life-threatening complication, though four patients required additional surgical interventions.

The study wasn’t powered to look for differences between the surgical arms or for clinical outcomes, though cardiovascular risk factors did improve.

Limitations included the short follow-up and the open-label assessment of patients at a single center.

Italian Experience

The second trial, led by Geltrude Mingrone, MD, of the Catholic University of Rome, was likewise a single-center, unblinded trial randomizing patients to gastric bypass, biliopancreatic diversion, or conventional medical therapy alone by a team comprised of a diabetologist, a dietitian, and a nurse.

The 60 participants had a BMI of at least 35 kg/m² and diabetes of at least 5-years duration with an hemoglobin A1c of 7.0% or more (mean 9%).

The likelihood of a diabetes remission by 2 years was 7.5 times higher for the gastric bypass group and 9.5 times higher for the biliopancreatic-diversion group even assuming the best case scenario that the two medication-group patients who dropped out had a diabetes remission (bothP<0.001).

Average reduction in hemoglobin A1c from baseline was 43% in the biliopancreatic-diversion group and 25% in the gastric-bypass group compared with just 8% in the medical therapy group, with all comparisons statistically significant.

Weight reductions came out similar at 2 years between surgery types at 33% to 34% of body weight from baseline compared with just 5% on medical therapy alone (both P<0.001).

BMI dropped from a mean of 45 down to 29 kg/m² in both surgery groups but from 46 to 43 kg/m²in the medical-therapy group.

But the glycemic benefit appeared independent of both weight loss and preoperative BMI, the researchers noted.

Lipids and blood pressure also improved more with bariatric surgery.

No patients died with bariatric surgery, but there was one case of an incisional hernia requiring reoperation 9 months later with biliopancreatic diversion and one intestinal obstruction requiring reoperation 6 months after gastric bypass. Two medical-therapy group patients had persistent diarrhea that resolved with substitution of another drug in place of metformin.

Limitations included the small sample size and lack of power for safety and clinical endpoints.

Bariatric surgery isn’t without hazards and remission may not be a cure, but it is gaining recognition in management of diabetes, the editorialists noted.

International Diabetes Federation now calls it appropriate for obese patients with type 2 diabetes not getting to glucose control targets with available medical therapy, especially with concomitant hypertension or other major coexisting illnesses.

“The final question, which is as yet untested, is whether bariatric surgery is suitable for all obese patients with type 2 diabetes, even those with a lower body-mass index,” they wrote