The beneficial effects of bariatric surgery on glycemic control in obese patients with type 2 diabetes are durable out to at least five years, with the advantage over intensive medical therapy appearing to widen over time.
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That’s the key takeaway of the final, five-year follow-up report from the pivotal STAMPEDE trial, which was presented April 4 by Cleveland Clinic bariatric surgeon Philip Schauer, MD, as a late-breaking trial at ACC.16, the American College of Cardiology’s 65th Annual Scientific Session.
“Our findings show continued durability of glycemic control after metabolic surgery as well as persistent weight loss and reductions in diabetes and cardiovascular medications at five years,” says Dr. Schauer.
Interim analyses confirmed
STAMPEDE is a three-arm controlled trial conducted at Cleveland Clinic that randomized 150 obese patients with type 2 diabetes to intensive medical therapy alone or in combination with plus Roux-en-Y gastric bypass or sleeve gastrectomy. Findings from the new prespecified five-year follow-up confirm those from the one-year and three-year reports and include the following:
- Rates of achieving and maintaining an HbA1c level of 6.0 percent or less at five years were significantly higher with gastric bypass (29 percent) and sleeve gastrectomy (23 percent) than with intensive medical therapy alone (5 percent) (P < .02 for each surgical group vs. medical therapy). The absolute reduction in HbA1c was 2.1 percentage points among surgically treated patients vs. 0.3 percent in those receiving medical therapy alone (P ≤ .001).
- Mean percentage weight loss was significantly greater with gastric bypass (–22 ± 8.3 percent) and sleeve gastrectomy (–19 ± 6.6 percent) than with medical therapy (–5 ± 9.9 percent).
- Use of cardiovascular and glucose-lowering medications, including insulin, at five years was significantly reduced from baseline in both surgical groups, and was significantly lower in the surgical groups than in the medical therapy group. Over 88 percent of surgically treated patients maintained glycemic control without use of insulin.
New insights at five years
The five-year analysis also yielded several new insights, including the following:
- In the two surgical groups, achieving the primary end point of an HBA1c ≤ 6.0 percent was predicted both by a reduction in body mass index (BMI) and a duration of diabetes of less than eight years.
- There were no late major complications of surgery except for one reoperation (a successful laparoscopic conversion of sleeve gastrectomy to gastric bypass for recurrent gastric fistula) four years after randomization.
- Significant and durable improvements in bodily pain and general health were demonstrated using a validated quality-of-life instrument in both surgical groups relative to the medical group.
- Several biomarkers associated with heightened cardiovascular risk were reduced in the surgical arms, but no beneficial effects on retinopathy or nephropathy were seen at five years.
“Some advantages of gastric bypass over sleeve gastrectomy have emerged during follow-up,” Dr. Schauer adds. “At five years, gastric bypass maintained greater weight loss than sleeve gastrectomy while requiring fewer medications.”
The single-center study was coordinated by the Cleveland Clinic Coordinating Center for Clinical Research (C5Research).
Implications for guidelines?
He also notes that the final STAMPEDE results might help expand the population of patients in whom bariatric surgery may be considered for improving glycemic control. “Most clinical guidelines and insurance policies for bariatric surgery limit access to patients with a BMI of 35 or above,” Dr. Schauer says. “But our five-year results demonstrate that glycemic improvement in patients with a BMI of 27 to 34 is durable at least out to five years.”
Risk/benefit balancing still imperative
Despite these confirmatory final results, the STAMPEDE trial should be considered in context by clinicians, points out STAMPEDE co-investigator Sangeeta Kashyap, MD, a Cleveland Clinic endocrinologist. “The superior benefits of surgery to attain diabetes treatment goals must be carefully balanced with the long-term risks associated with surgery for individual patients,” she says.
Dr. Schauer adds that STAMPEDE was not large enough or long enough to detect differences in cardiovascular complications: “The potential benefits of bariatric surgery on clinical end points can be assessed only through large multicenter trials.”
Click here to view more late-breaking trials and clinical research from ACC.16