1. Bariatric surgery significantly reduced and sustained glycated hemoglobin (HbA1c) levels compared to medical therapy at five-year follow-up.
2. Both gastric bypass and sleeve gastrectomy were associated with a significantly higher degree of sustained weight loss, reduced use of cardiovascular and glucose-lowering medications, and improvement in quality of life (QOL) compared to medical therapy.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Four years ago, researchers from the STAMPEDE trial first reported reductions in HbA1c in type 2 diabetic patients with mild to moderate obesity who underwent bariatric surgery. These findings were then confirmed in the three-year follow-up. Since then, a growing number of unblinded trials have demonstrated the superiority of bariatric surgery compared to medial therapy in glucose control and sustained weight loss. This final report is the five-year follow-up from the landmark STAMPEDE trial. The primary outcome – sustained HbA1c of 6.0% of less – was significantly more likely in both the gastric-bypass group and sleeve-gastrectomy group compared with medial therapy. Among secondary outcomes, bariatric surgery demonstrated a significant improvement in weight reduction, lipid profiles, QOL, and reduced medication use. Though surgical risks must still be considered on an individual patient level, the results of this five-year trial support the role of bariatric surgery as an early and primary treatment option for type 2 diabetes in patients with mild to moderate obesity.
This is the largest and longest randomized trial to compare bariatric surgery and medical therapy in patients with diabetes. However, the sample size and duration are still inadequate to detect long-term differences in the rate of possible end-organ sequelae. The potential benefits of bariatric surgery on clinical end-points such as cardiovascular mortality, retinopathy, and nephropathy require larger, multicenter trials for evaluation.
In-Depth [randomized controlled trial]: This was a three-group, randomized, controlled, non-blinded, single-center trial that assigned 134 patients with a body-mass index (BMI) of 27 to 43 to gastric bypass, sleeve gastrectomy, or medical therapy in a 1:1:1 ratio. The primary outcome was a HbA1c level of 6.0% or less with or without the use of diabetes medications. Prespecified secondary outcomes included measures of glycemic control, weight loss, blood pressure, lipid levels, renal function, ophthalmologic outcomes, medication use, adverse events, and quality of life.
The rate of achieving and sustaining HbA1c levels at or below 6.0% was significantly higher in both gastric bypass (29% vs. 5%; p = 0.01) and sleeve gastrectomy (23% vs. 5%; p = 0.03) compared to medical therapy. After adjusting for multiple comparisons, these P-values were changed from 0.01 and 0.03 to 0.03 and 0.07, respectively. A duration of diabetes for less than 8 years was also found to be the main predictor of a lowered and sustained HbA1c. Sustained weight loss was significantly higher in both surgical groups compared to medical therapy (p < 0.05), with the reduction in body weight greater in the gastric bypass group versus sleeve gastrectomy (p = 0.01). Among other secondary outcomes, there were significant improvements in pain and quality of life based on validated surveys (p < 0.05 for all comparisons) and a significant reduction in cardiovascular disease biomarkers in the surgical groups (triglycerides, high-density lipoprotein). Late surgical complications included one late reoperation and mild anemia. No significant differences were noted in blood pressure, ophthalmologic, or renal outcomes. Results were similar in patients with a BMI both above and below 35 and confirm findings from the STAMPEDE trial’s one-year and three-year reports.
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