Health technology assessment of bariatric surgery in morbidly obese patients in Spain

Obesity is associated with many risks for health. Bariatric surgery is seen as a valid option for patients with morbid obesity (BMI ≥ 40) who do not respond to non-surgical treatment.

The authors have conducted a systematic review of the literature, together with a meta-analysis of the evidence available on the efficacy, safety and cost-effectiveness of bariatric surgery in people with obesity compared with non-surgical treatment (diet and/or pharmacotherapy). Furthermore, this report includes analysis of the evidence for patients with both obesity and diabetes, along with a comparative analysis of the evidence on the efficacy, safety and cost-effectiveness of the various forms of bariatric surgery. The assessment of the evidence obtained was performed following the GRADE methodology.

More than thirty (30) randomized clinical trials (RCTs) were identified, all of which provided information on at least one of the following outcomes of bariatric surgery: changes in BMI or weight; relevant side effects and/or complications; and, in the case of patients with diabetes, information on the impact of surgery on the remission of the disease. The authors note that these studies have several limitations. For example, these RCTs were relatively short in time, and in their samples were generally low. Thus the studies may lack statistical power. Also, these studies had short follow-up periods; this may bias the conclusions since sometimes results are seen only after a more extended period.

Bariatric surgery versus non-surgical treatment (diet and/or pharmacotherapy)

Thirteen (13) RCTs with relatively small sample sizes and a moderate risk of bias (low-moderate quality of data) were considered for this case. The studies show that surgery is generally more effective than non-surgical treatment for achieving clinically relevant reductions in both weight and BMI. But, as the follow-up time of these studies is not longer than 5 years, it cannot be concluded whether these effects are maintained over the long term.

Data from Spanish Bariatric Surgery Registry indicate that 3 out of every 1000 patients died in the first month of follow-up after surgery in Spain before the end of 2014.

Other studies, which included obese patients with diabetes type 2, prove that surgery presents better short-medium term results than non-surgical treatment for weight and BMI, but has worse outcomes in terms of treatment side effects.

One Spanish cost-utility study, which compared costs and effects after five years of follow-up in patients undergoing bariatric surgery or non-surgical treatment, estimated an added cost of 1456 euros per QALY for patients treated with the gastric band and 2664 euros per QALY for patients treated with gastric bypass.

Gastric bypass versus sleeve gastrectomy

Ten (10) relatively low-quality RCTs provided evidence regarding this matter. No significant differences were found between the two methods. A minimal difference is showed in the patients with type 2 diabetes (bypass achieves 1 point reduction in BMI, but it probably has small clinical repercussion). No significant differences regarding the remission of diabetes are demonstrated.

Gastric bypass versus adjustable gastric band

Four (4) moderate-quality studies found that the bypass was much more effective than the adjustable gastric band in achieving significant decreases in BMI (mean reductions of five points) and weight (mean reductions of 18 kg). In Spain, according to a European-wide study, a cost per QALY is 1456 euros for the gastric band and 2664 euros for gastric bypass.

Gastric bypass versus biliopancreatic diversion

No significant difference between the two treatments was found, according to three (3) RCTs of very poor quality.

Conclusion

Bariatric surgery is more effective than non-surgical therapy for obtaining clinically relevant reductions in weight and BMI or for achieving remission of diabetes, in morbidly obese patients. However, the authors note the need for further studies that need to confirm whether these differences are maintained in the long run.

See the full report in Spanish (with summary in English) here.

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