by Jason Block, MD, MPH
VBLOC is approved based on randomized controlled trial
Does it work? The first study of it enrolled 294 patients, with 2/3 in the active treatment arm and 1/3 in a sham control arm. Sham participants had the generator and leads implanted but the device generated only minimal electrical impulses. After one year, weight loss was 17% of excess body weight in those actively treated and 16% in those in the control group. No statistical difference. Patients who used the device more (activation of the device required patients to wear an external controller) lost more weight.
A more recent study, this time with an updated device that provided 12 hours of stimulation without wearing an external controller, enrolled 239 patients. Again 2/3 received active treatment and 1/3 sham. This time, the sham control group did not have leads implanted but only a generator in the chest wall. At one year, those in the treatment arm lost 24% of excess body weight (9% of initial body weight) compared to 16% (6%) in the sham group. This was a significant difference though failed a pre-specified expected difference between treatment and control of 10%. Because of reasonable safety results (about 9% had a serious adverse events, with most of these related to the surgery itself), the FDA still approved the device for people with a BMI of 40 to 45 kg/m2 or 35 to 39.9 with an obesity-related comorbidity, such as diabetes, hypertension, or high cholesterol. The FDA also was reassured that the weight loss appeared to be maintained for the 18 months over which patients were followed.
FDA approves but does it make sense for patients?
We also don’t know long-term results from VBLOC. Upon approval, the FDA required the manufacturer to conduct 5-year studies to assess long-term effectiveness and safety. Based on the 18 month data, the company estimated that ½ of patients would have their device extracted at 5 years, not a trivial amount. The expectation would be that many patients will regain any weight loss if they no longer have the device. If they want to keep the device active, eventually, all patients may have to undergo repeat surgeries to replace the device.
VBLOC has its advocates, with many stating that it provides one more option for patients with obesity. Like others, I’m a skeptic that VBLOC serves much of a role, if any. Weight loss with VBLOC, when compared to control groups, appears to be less than phentermine/topiramate, liraglutide, and naltrexone/bupropion. And, we haven’t yet seen any other benefits in metabolic or cardiovascular risk. Intensive lifestyle treatments achieve weight loss and metabolic benefits that are better, when compared to control groups. VBLOC seems less effective than alternatives yet is more costly and requires a surgery.
With all treatments for obesity, we are in desperate need of information about which patients benefit most from each treatment modality. With information like this, we might find a narrow subset of patients for whom VBLOC will be useful. We may even learn this with the 5 years trials that will be conducted. I will encourage my patients to stick with other treatments until then.