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Cost-Effectiveness Analysis of Vagal Nerve Blocking for Morbid Obesity
Jeffrey C. Yu, AB; Bruce Wolfe, MD; Robert I. Griffiths, ScD, MS; Raul Rosenthal, MD; Daniel Cohen, MA; and Iris Lin, PhD
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Cost-Effectiveness Analysis of Vagal Nerve Blocking for Morbid Obesity

Jeffrey C. Yu, AB; Bruce Wolfe, MD; Robert I. Griffiths, ScD, MS; Raul Rosenthal, MD; Daniel Cohen, MA; and Iris Lin, PhD
This lifetime economic analysis demonstrates vagal nerve blocking therapy to be a cost-effective alternative to conventional therapy in class 2 and 3 obesity patients.
ABSTRACT

Objectives: To assess the lifetime cost-effectiveness of intermittent, reversible vagal nerve blocking (via the implantable weight loss device vBloc) therapy versus conventional therapy as treatment for patients who are class 2 obese with diabetes and for those who are class 3 obese with or without diabetes, who have found pharmacotherapy and behavioral therapies ineffective, but are not prepared or willing to undergo current bariatric surgical options.

Study Design: A cost-effectiveness model was designed to simulate weight loss, diabetes remission, and costs in patients with obesity undergoing vagal nerve blocking therapy versus conventional therapy.

Methods: The model compared 2 treatment arms, vagal nerve blocking therapy and conventional therapy, and for each treatment arm included 4 health states based on body mass index (BMI) class. Using Monte Carlo simulation, patients entered the model one at a time and could transition between health states by experiencing BMI change. The model focused on change in BMI and diabetes remission as predictors of healthcare costs, health-related quality of life, and survival. Inputs for vagal nerve blocking effectiveness were obtained from the ReCharge trial; however, remaining inputs were estimated from published literature. Incremental cost-effectiveness ratios (ICERs) were evaluated in terms of cost per quality-adjusted life-year (QALY) gained.

Results: ICERs for vagal nerve blocking versus conventional therapy in patients who were class 2 and class 3 obese were estimated to be $17,274 and $21,713 per QALY gained, respectively. Sensitivity analyses showed results to be robust to reasonable variation in model inputs, with the upper limit of ICERs remaining below $30,000 for all sensitivity analysis scenarios assessed.

Conclusions: Vagal nerve blocking therapy provides a cost-effective alternative to conventional therapy in patients who are class 2 obese with diabetes and in those who are class 3 with or without diabetes.
Takeaway Points

Vagal nerve blocking therapy is a minimally invasive alternative to conventional therapy for the treatment of obesity and is positioned for patients who have found pharmacotherapy and behavioral therapies ineffective, but are not prepared or willing to undergo current bariatric surgical options. 
  • A lifetime cost-effectiveness analysis of vagal nerve blocking versus conventional therapy in patients with class 2 and class 3 obesity was conducted.
  • Patients experienced incremental cost-effectiveness ratios less than $30,000 in base and sensitivity analyses, demonstrating vagal nerve blocking therapy to be cost-effective relative to conventional therapy. 
  • Model design incorporated both body mass index class stratification and diabetes remission, and simulated cost and quality-adjusted life-year outcomes.
It is estimated that more than one-third (34.9%) of adults in the United States are obese, with 8.8% considered class 2 obese (body mass index [BMI] = 35.0-39.9) and 6.0% considered class 3 obese (BMI ≥40.0).1 Lifestyle modifications, in the form of changes in food intake and activity level, and pharmaceutical therapy provide modest weight loss and have been demonstrated to be effective for some patients.2,3 At present, bariatric surgery has proven to be the most effective treatment option for significant weight loss and improvement in health.4

Although bariatric surgery has demonstrated clinical efficacy in treatment of morbid obesity, recent evidence suggests that only a small percentage of patients who qualify for and would benefit from bariatric surgery ever undertake this mode of therapy.5 According to the results of one study published in 2015 using the 2007 to 2012 National Health and Nutrition Examination Survey (NHANES) database, it was estimated that as many as 15% of US adults (32 million) may be eligible for bariatric surgery based on the 2013 Guideline for the Management of Overweight and Obesity in Adults.6 However, according to the American Society for Metabolic and Bariatric Surgery (ASMBS), in 2013, only 179,000 bariatric surgical procedures were performed—a figure that is significantly below the number of potentially eligible candidates.6,7

Another consideration for bariatric surgery is the associated mortality over time, with 1-year mortality at 2.4% and 5-year mortality at 6.4% for US adults. Adjusted analyses found no significant association between bariatric surgery and all-cause mortality in the first year of follow-up and significantly lower mortality at 5 and 10 years of follow-up.8 The gap in adoption of surgical treatments presents an opportunity to evaluate other low-risk, well-tolerated, and minimally invasive weight loss treatments.

The unmet need in current weight loss options is also associated with significant economic cost burden. Between 1998 and 2006, the annual medical cost burden of obesity increased from 6.5% to 9.1% of annual medical spending in the United States.9 In 2008 US dollars, the economic burden of obesity in the United States was estimated to be $147 billion per year.9 The current treatment gap in obesity, as well as the growing economic burden, has created meaningful value in the development and economic assessment of low-risk, well-tolerated, and minimally invasive treatment options.

One such option is vagal blocking using electrodes implanted through laparoscopic surgery. The Safety and Efficacy of vBloc Therapy Delivered by the Maestro Rechargeable System for the Treatment of Obesity (ReCharge) trial, a multicenter, randomized trial, evaluated vagal nerve blocking (via the implantable weight loss device vBloc) therapy through a sham-control design. This type of therapy uses a unique intermittent, vagal nerve blocking method to affect the perception of hunger and fullness and is delivered by a pacemaker-like device.10 The device is implanted through minimally invasive laparoscopic surgery and uses electrodes to block neural signal transmission to the vagus nerve,10 which is known to play a key role in satiety, metabolism, and autonomic control in upper gastrointestinal tract function.11 Vagal nerve blocking therapy is a reversible procedure and one that is neither anatomy altering nor restricting.10 According to the ASMBS position statement, it has demonstrated statistically significant excess weight loss in the short term and a low incidence of severe adverse events (AEs) and revision.12

Compared with more invasive bariatric alternatives, vagal nerve blocking therapy provides a durable and less invasive weight loss therapy option, with a strong safety profile.10 Other available minimally invasive weight loss procedures include gastric balloon and gastric banding. Relative to gastric balloon therapy, in which the device is removed at or within 6 months of placement,13,14 vagal nerve blocking presents a durable and longer-term treatment option. In addition, the safety and efficacy of balloon therapy beyond 6 months have not been established. Further, the intent of the gastric balloon therapy is to offer a replacement balloon following the required removal at 6 months, for a potentially indefinite length of time. Even though gastric banding presents a similar perioperative safety profile as a vagal nerve blocking device, it is associated with high rates of reoperation15 and late complications, such as band slippage and pouch dilation,16 and in recent years, rates of use have declined. Among bariatric surgeries, the proportion of gastric banding surgeries decreased from 35.4% in 2011 to 14.0% in 2013.17

The objective of this study was to assess the cost-effectiveness of vagal nerve blocking versus conventional therapy. The population of interest was defined as individuals who had not been successful with behavioral therapy or pharmacotherapy and who sought an alternative that was cost-effective, minimally invasive, and demonstrated favorable comparative safety. Findings presented in this paper add to the current literature by providing insight into the cost-effectiveness of a newer mode of obesity treatment (vagal nerve blocking therapy) versus conventional therapy.

METHODS

Model Overview


This cost-effectiveness model was developed in TreeAge Pro 2014 (TreeAge Software, Inc; Williamstown, MA), and it was designed to compare the vagal nerve blocking device with conventional therapy in patients who are class 2 obese with diabetes and those who are class 3 with or without diabetes. The model contained 4 BMI health states: not obese (<30 kg/m2), class 1 obesity (30.0-34.9 kg/m2), class 2 obesity (35.0-39.9 kg/m2), and class 3 obesity (≥40 kg/m2). Through Monte Carlo simulation methods, patients were modeled one at a time18 and transitioned between health states by experiencing BMI change based on the treatment arm. Patients were tracked throughout the model and accumulated costs and utilities associated with their BMI levels. At the end of the model, incremental cost-effectiveness ratios (ICERs) were presented as cost per quality-adjusted life-years (QALYs) gained.

Model Structure

The model compared 2 treatment arms—vagal nerve blocking and conventional therapy—over a lifetime horizon. As described previously, vagal nerve blocking therapy is a minimally invasive bariatric surgical option. Conventional therapy, in the form of lifestyle counseling, was selected as the comparator for vagal nerve blocking therapy, as candidates for this type of therapy were patients who had not been successful in losing weight under medical management (eg, pharmacotherapy) and were not willing or ready to undergo other bariatric surgical options. Other minimally invasive weight loss procedures include gastric balloon and gastric banding. However, balloon therapy was not included in the model as its safety and efficacy beyond 6 months had not been established. Gastric banding was excluded as a comparator because its use has decreased substantially in recent years.

The model was built on change in BMI and diabetes status as predictors of cost and health-related quality of life. Over the course of the model, patients could experience BMI change, diabetes remission, and mortality. Costs and utilities were associated with BMI, and over the course of the model, patients accumulated costs and utilities by remaining in, or transitioning from, various BMI levels.

Each treatment arm was associated with the 4 BMI health states previously mentioned. At model entry, patients undergoing vagal nerve blocking and conventional therapy were placed in initial BMI health states according to their baseline BMI, which was determined by mean class 2 and class 3 BMIs in the ReCharge trial. Experiencing change in BMI allowed patients to transition between BMI health states. Diabetes and diabetes remission were also incorporated in the model structure. At baseline, patients were assigned an initial diabetes status according to their initial BMI health state, based on the indication explored in the ReCharge trial. In subsequent model cycles, patients were assigned a probability of diabetes remission, which was a function of the BMI trajectory associated with the treatment arm. The vagal nerve blocking device model also incorporated device replacement, as well as revision surgeries associated with both initial and device replacement implantations.

The final health state was death, for which a probability derived from the literature was applied at the end of each cycle. Patients remained in the model until death or age 100, whichever occurred first. A schematic of the model health states and transitions are provided in Figure 1.

Model Process

At model entry, patients were assigned ages from a sampled distribution (mean = 47; standard deviation [SD] = 10) and sent through the model one at a time to receive vagal nerve blocking and conventional therapy in separate but parallel simulations. The age distribution was selected to align with the ReCharge trial population.10 Patients entering the model in class 2 and class 3 were assigned baseline BMIs of 37.5 and 42.5, respectively, according to the ReCharge trial, and placed in corresponding class 2 obesity and class 3 obesity initial health states. All class 2 patients were then assigned the variable of diabetes in the first cycle, and those in class 3 were assigned a probability of having diabetes, as per the indication evaluated in the ReCharge trial. Also, a probability of device revision surgery was assigned to patients in the nerve blocking arm.

As patients cycled through the model, they could experience change in BMI (specific to class 2 or 3) as per the BMI trajectory from the ReCharge trial and were able to transition between health states. As the ReCharge trial provided BMI change data for up to 30 months, it was conservatively assumed that BMI change beyond 30 months was flat. Conventional therapy patients did not experience BMI change, an assumption previously implemented in bariatric surgery cost-effectiveness analyses by Ackroyd et al.19

Additionally, patients were given the probability of experiencing diabetes remission during each cycle, which was BMI-driven, and as such, diabetes remission could not occur in the vagal nerve blocking therapy arm. It was assumed that patients who had experienced diabetes remission remained diabetes-free for the remainder of the model. At the end of each cycle, patients were assigned a probability of death. Those who survived in a given cycle continued to the next cycle. At the end of 9 years, the patients receiving vagal nerve blocking therapy who remained in the model were given a device replacement, and a probability of device revision surgery was applied to those who received a replacement. Patients were tracked throughout the model and were assigned literature-based costs and utilities associated with their BMI level and diabetes status for each cycle. Costs and utilities were then aggregated at the end of each patient’s journey through the model.

Model Inputs

Model inputs included in the analysis are presented in Table 1 and were derived from the scientific literature, ReCharge trial, and publicly available databases.

BMI trajectory. Data for baseline BMI and BMI change for patients in the class 2 and class 3 analyses came from the ReCharge trial. Mean percent change in BMI was calculated for class 2 patients and class 3 patients on a weekly basis.

 
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