Cost-Effectiveness of Laparoscopic Gastric Banding and Bypass for Morbid Obesity

Objective:

To assess the cost-effectiveness of laparoscopic adjustable gastric banding (LAGB) and laparoscopic Roux-en-Y gastric bypass (LRYGB) as treatment for morbid obesity.

Study Design:

A Markov model was developed to simulate weight loss, health consequences, and costs for surgical treatment of morbid obesity. The model was used to estimate incremental cost-effectiveness ratios (ICERs) in terms of cost per quality-adjusted life-year (QALY) gained.

Methods:

Estimates of procedure effectiveness were derived from published results of a head-to-head randomized controlled trial. Other model parameters, including complication rates, costs of treatment, adverse events and obesity, mortality rates, and utilities, were estimated from published literature and publicly available databases. Costs (2006 US dollars) and QALYs were discounted by 3% per annum.

Results:

Under conservative assumptions, both LAGB and LRYGB improved health outcomes, at a higher cost, compared with no treatment. ICERs for both LAGB and LRYGB versus no treatment were below $25,000 per QALY gained. ICERs were lower for individuals with higher initial body mass index and higher for older individuals. ICERs for men were generally higher than those of women. Sensitivity analyses showed these results to be robust to reasonable variation in model parameters and overall parameter uncertainty. Base-case ICERs for LRYGB versus LAGB were below $25,000 per QALY gained, but were highly sensitive to model assumptions.

Conclusion:

Both LAGB and LRYGB provide significant weight loss and are cost-effective compared with no treatment at conventionally accepted thresholds for medical interventions.

(Am J Manag Care. 2010;16(7):e174-e187)

The majority of bariatric procedures in the United States are laparoscopic Roux-en-Y gastric bypass (LRYGB) and laparoscopic adjustable gastric banding (LAGB).

• Both LAGB and LRYGB lead to better healthcare outcomes and higher costs compared with no treatment. In the main analysis, LAGB results in less weight loss than LRYGB, but is associated with lower costs.
• Both LAGB and LRYGB are cost-effective alternatives to no treatment, with incremental cost-effectiveness ratios below $25,000 per quality-adjusted life-year gained; results are robust.
• Estimates of the cost-effectiveness of LAGB versus LRYGB are sensitive to assumptions about maintenance of weight loss in the medium to long term; long-term comparative studies of the 2 procedures are needed.

Obesity, or excessive body fat, is a major risk factor for a host of detrimental medical conditions including type 2 diabetes, hypertension, dyslipidemia, osteoarthritis, and obstructive sleep apnea.1 Approximately 5.7% of American adults (>12 million people) are morbidly obese,2 with a body mass index (BMI) of >40 kg/m².

There are 3 established approaches to treating morbid obesity: lifestyle modification, pharmacologic therapy, and surgery. The first 2 approaches have been shown to have a limited impact on long-term weight control.^3,4 The third option, bariatric surgery, has been shown to be an effective long-term treatment for morbid obesity, with mean excess weight loss exceeding 60%.⁵ However, the risks of complications with bariatric surgery are not trivial.⁶

The majority of bariatric surgeries currently performed in the United States are laparoscopic Roux-en-Y gastric bypass (LRYGB) procedures. An alternative to gastric bypass is laparoscopic adjustable gastric banding (LAGB), in which a silicone elastomer ring is placed around the upper part of the stomach, creating a new small stomach pouch so the food storage area in the stomach is reduced. Excess weight loss with LAGB, although significant, may be lower than that seen with LRYGB.⁶ However, LAGB, unlike LRYGB, does not involve stapling or partition of the stomach or intestine; thus, postoperative complication rates are lower, hospitalizations are shorter, and there is less risk of micronutrient deficiency compared with LRYGB.⁷ Moreover, the procedure is fully reversible. The objective of this study is to assess the cost-effectiveness of LAGB versus that of LRYGB, or no treatment, for patients with morbid obesity.

METHODS

Model Structure

We constructed and estimated a Markov model of treatment and outcomes for obese adults. The model focused on decreases in BMI and treatment-related adverse events as predictors of lifetime cost, health-related quality of life, and survival. Patients received initial treatment with LAGB or LRYGB, or received no treatment. After the initial treatment period, patients entered the Markov model in 1 of the 5 health states corresponding to their initial BMI status: not obese (BMI <30 kg/m²); obese (BMI 30-34.9 kg/m²); morbidly obese I (BMI 35-39.9 kg/m²); morbidly obese II (BMI 40-49.9 kg/m²); and super obese (BMI >50 kg/m²). The sixth health state in the model was death. Health states were associated with specific treatment costs, levels of “other” health expenditures, health-related quality of life, and mortality risks. Patients transition between Markov states by changing BMI status (losing or gaining weight) or dying. For the first 10 years of the model, surgical patients remained at risk of transient treatment-related adverse events that may be mild, moderate, or severe.

Model Estimation

Table 1

We estimated model probabilities, costs, and utilities from a variety of published and publicly available sources, supplemented by input from a clinical expert in minimally invasive (laparoscopic) bariatric surgery. reports model parameters and data sources.

Target Population. The population for this analysis was limited to adults age 18 to 74 years who satisfied the clinical eligibility criteria for bariatric surgery: BMI >40 kg/m² or BMI >35 kg/m² with comorbid conditions.⁸

Figure 1

Treatment Efficacy. Probabilities of treatment-related weight loss were estimated from a prospective study by Angrisani et al, in which morbidly obese patients were randomized to LAGB and LRYGB and followed for 5 years postsurgery.⁹ In base-case analyses, it was assumed that BMI remained constant after the 5-year follow-up period. Patients receiving no treatment were assumed to maintain a constant BMI for the duration of the model. The study by Angrisani et al was judged to be the strongest available based on its randomized head-to-head design and minimal attrition over the 5-year study period. The study limitations include a small initial sample (N = 51) and a European rather than US setting. For this reason, we also estimated the model using an alternative source for 5-year efficacy data: a systematic review of 36 English-language studies of weight loss outcomes following LAGB or LRYGB by O’Brien et al.¹⁰ Limitations of the O’Brien et al study include a preponderance of single-armed rather than comparative studies, and attrition rates that may have been underreported. Compared with the Angrisani et al study, O’Brien et al reported greater effectiveness for LAGB and shorter durability of weight loss for LRYGB (with weight regain beginning in year 3), as shown in .

Appendix A

The calculation of transition probabilities between BMI categories also is described in .

Probabilities of Treatment-Related Adverse Events. The estimated incidences of adverse events were derived from a comparative study of the complications of LAGB and LRYGB by Parikh et al.¹¹ Events are classified by severity: major reoperations, defined as organ repairs such as resection of the bowel; moderate reoperations, defined as operations not requiring organ repair (eg, laparoscopic repositioning of a gastric band); and medical treatment, defined as drug therapy only (eg, antibiotic therapy for an infection). Parikh et al reported separate estimates for the probabilities of major reoperations and all adverse events for the first 30 days (early) and after 30 days (late). We estimated the early and late probabilities of moderate reoperations and medical treatments based on the relative proportions of total early and total late complications from that study. The average period of follow-up was approximately 12 months; we assumed that the yearly probability of surgical adverse events remained constant for the first 4 years postsurgery, was halved for years 5 to 10, and was zero after 10 years. Consistent with the literature, patients receiving no treatment were assumed to have no serious adverse events.

Mortality. Patients undergoing LAGB or LRYGB have a 1-time probability of postoperative death from surgery in the first 30 days.¹² BMI-specific mortality rates were estimated based on age- and sex-specific all-cause mortality rates derived from US life tables,¹³ to which we applied BMI-specific relative risk ratios from an analysis of the National Health and Nutrition Examination Survey by Flegal et al.¹⁴ Because Flegal et al reported a single aggregated mortality risk ratio for BMI >35 kg/m², we estimated separate mortality risk ratios for the morbidly obese I, morbidly obese II, and super obese groups using linear extrapolation based on the trends at lower levels of BMI and the relative prevalence of morbid obesity categories reported by Sturm: morbidly obese I (67%), morbidly obese II (29%), and super obese (4%).¹⁵

Costs. The physician costs for the LAGB and LRYGB procedures were estimated using Current Procedural Terminology codes: 43770, 90772, 90801, 97802, and 99214 for LAGB; and 43644, 90801, 97802, and 99214 for LRYGB.¹⁶ Associated inpatient costs were estimated using data from the Healthcare Cost and Utilization Project (HCUP) Database with International Classification of Diseases, Ninth Revision codes: 44.95 for LAGB, and 44.38 for LRYGB.¹⁷ The hospital charges were converted to resource costs using hospital cost-to-charge ratios published in the HCUP Database. The default schedule of follow-up visits was based on treatment guidelines of the American Society for Metabolic and Bariatric Surgery, supplemented by input from our clinical expert as: 9 visits in year 1, 2 visits in year 2, and 1 annual visit thereafter for LAGB; and 6 visits in year 1, 2 visits in year 2, and 1 annual visit thereafter for LRYGB.

In consultation with our clinical expert, the costs of LAGB- and LRYGB-related adverse events for each level of severity were estimated using the Physician Fee Guide (physician costs),¹⁶ HCUP Database (facility costs),¹⁷ and the Red Book (drug costs).¹⁸ Within each severity category, a weighted average cost was derived, based on the relative prevalence of such complications as reported by Jan et al,¹⁹ supplemented by additional input from the clinical expert. The cost of a postoperative fatality was assumed to be equal to that of an early major reoperation. A list of the complications that were used to generate the weighted average costs is available from the authors on request.

"Other" medical expenditures specific to each BMI level were calculated based on a study of the Medical Expenditure Panel Survey by Arterburn et al.²⁰ Because this study reported aggregated expenditures for the BMI >40-kg/m² group as a whole, we estimated the other medical costs for the morbidly obese II and super obese groups using linear extrapolation as described above.¹⁵ Where necessary, costs were updated to 2006 US dollars using the Medical Care Services component of the Consumer Price Index.

Health-Related Quality of Life. Estimates of BMI-specific utilities were derived from a regression analysis of EQ-5D data from the 2000 Medical Expenditure Panel Survey by Jia and Lubetkin,²¹ rescaled to replicate the US mean population EQ-5D score of 0.868 as reported by Sullivan and Ghushchyan.²² Jia and Lubetkin reported mean utilities for individuals with BMI >35 kg/m² as a single group. We used linear extrapolation to estimate separate utilities for the morbidly obese I, morbidly obese II, and super obese groups, as described above.

No estimates of bariatric-surgery—specific utility decrements were identified in the literature. Estimated utility decrements for the LAGB and LRYGB procedures therefore were derived from utilities reported for laparoscopic surgery for hernia repair in the United Kingdom,²³ rescaled to apply to the US population.²² The utility decrement was applied at the time of surgery for 4 weeks for LAGB and 6 weeks for LRYGB, to reflect the slightly longer recovery time associated with LRYGB compared with LAGB. The utility decrement for a major reoperation was estimated as the decrement associated with a hysterectomy²⁴ and was applied for 6 weeks. The decrement for a moderate reoperation was estimated as the decrement associated with laparoscopic hernia repair²⁴ and was applied for 4 weeks. The decrement for medical treatment was estimated as the mean of the decrements associated with venous thrombosis, gastroesophageal reflux disease, ulcer, and gastritis as reported by Sullivan and Ghushchyan²⁵ and was applied for 4 weeks.

ANALYSES

Base-Case Analyses

Cumulative costs associated with morbid obesity and its treatment, survival in life-years, and quality-adjusted life-years (QALY s) were estimated for each obesity treatment strategy. Cumulative costs include costs of initial treatment, follow-up, and treatment-related adverse events minus cost offsets generated by decreases in other health expenditures as patients lose weight. The treatments were ranked in order of increasing costs and the incremental cost-effectiveness ratios (ICERs) were calculated by comparing the more costly with the less costly, dividing the incremental cost by the incremental benefit. The base-case analyses were stratified by sex and initial BMI category, assuming an initial age of 40 years. Results also were aggregated to the population level using a patient distribution consistent with the patient sample in the LAGB arm of the Angrisani trial (80% female; initial BMI: 23% morbidly obese I, 66% morbidly obese II, and 11% super obese).9 Cost-effectiveness analyses were performed from the perspective of a third-party payer over a lifetime horizon. All costs, life-years, and QALY s were discounted at an annual rate of 3%. Base-case analyses were performed using treatment efficacy parameters derived from the Angrisani et al study.

Alternate Scenarios and Sensitivity Analyses

Appendix B

We assessed the effect of uncertainty in comparative weight loss estimates by reestimating the model with an alternative source for efficacy estimates.10 In a second alternative analysis, patients were assumed to regain half of the cumulative BMI lost after 5 years over the following 5-year period. Multiple 1-way sensitivity analyses then were conducted to test the robustness of model results to changes in key parameters, particularly efficacy, rates of adverse events, and costs. Additional 2-way sensitivity analyses are discussed in .

Appendix C

A second-order probabilistic Monte Carlo sensitivity analysis was conducted to assess the sensitivity of study findings to overall parameter uncertainty, particularly with regard to treatment efficacy, rates of complications, costs, and utilities. We constructed a probability distribution for the estimates of treatment efficacy by bootstrapping the simulated LAGB and LRYGB cohorts—repeatedly sampling with replacement from each cohort of patients. Uncertainty in other key model parameters was characterized by probability distributions with means equal to the default estimates. Probabilities of adverse events were assumed to follow a beta (β) distribution, with distributional parameters reflecting the underlying trial samples. Estimates of treatment costs were assumed to follow a gamma (g) distribution with standard errors assessed, subjectively, as 10% of the mean value. The parameters and distributions of the variables included in the probabilistic analysis are summarized in .

RESULTS

Base Case

Table 2

Base-case results from the analysis using efficacy estimates derived from the article by Angrisani et al9 are reported in . Results of analyses are presented weighted over the patient population, and stratified by sex and initial BMI. Neither LAGB nor LRYGB is cost saving compared with no treatment; however, both LAGB and LRYGB are more beneficial than no treatment, providing an additional 2.04 (LAGB) and 2.9 (LRYGB) discounted lifetime QALY s for each treated patient. The ICERs for LAGB versus no treatment and for LRYGB versus no treatment are similar and relatively low (<$10,000 per QALY gained). Although LAGB costs an average of $5324 less than LRYGB in the aggregate population, it also is less effective, providing 0.42 fewer life-years saved and 0.86 fewer QALY s; the ICERs for LRYGB versus LAGB across patient groups lie below $15,000 per QALY gained. As the stratified results show, bariatric surgery is most cost-effective for females and for patients who have higher initial BMI. In addition, bariatric surgery is more cost-effective for younger patients (not shown).

Results for Alternate Scenarios and Sensitivity Analyses

For comparison, results of the analysis using the O'Brien et al data¹⁰ also are presented in Table 2. Under these alternative efficacy assumptions, both procedures remain cost-effective compared with no treatment, with ICERs less than $20,000 per QALY gained; however ICERs for LRYGB versus LAGB are significantly greater than those estimated using efficacy estimates from Angrisani et al.⁹

Table 3

reports the results of a series of 1-way sensitivity analyses for the default analysis based on efficacy estimates from Angrisani et al.⁹ We report the results for analyses for which the range in the relevant ICERs exceeds $1000. In all instances, the magnitude of the variation in the aggregate ICER is less than $10,000 per QALY gained, and the upper limits of our estimates of incremental cost-effectiveness for LAGB and LRYGB versus no treatment lie below $25,000 per QALY . The model was not sensitive to small changes in efficacy over the initial 10-year period. All ICERs for LRYGB versus LAGB fell below $15,000 per QALY .

However, in an analysis in which patients receiving LRYGB were assumed to partially regain weight over years 5 to 10 (as suggested by the O'Brien et al¹⁰ analysis), LAGB dominated LRYGB when using estimates of efficacy based on either Angrisani et al⁹ or O’Brien et al (not shown). When weight regain was modeled for patients receiving either LAGB or LRYGB, the ICER for LRYGB versus LAGB was $19,700 using estimates derived from Angrisani et al; however, LRYGB was dominated by LAGB using estimates derived from O'Brien et al.

Figure 2

illustrates the results of probabilistic sensitivity analysis that assessed the effects of uncertainty in the Angrisani and O’Brien—based analyses. One hundred percent of estimated ICERs for LAGB versus no treatment, and LRYGB versus no treatment, lay in the quadrant in which surgery is more expensive and more effective than no treatment, and below the $50,000 per QALY threshold line. The median costs per QALY gained for LAGB versus no treatment for the Angrisani and O’Brien analyses were $4700 (95% confidence interval [CI] = $1900, $7400) and $2900 (95% CI = $200, $5300), respectively. The analogous median ICERs for LRYGB versus no treatment were $4400 (95% CI = $1400, $7400) and $7200 (95% CI = $4000, $10,800). All estimated ICERs for LRYGB versus LAGB also fell below $50,000 per QALY for both analyses. In the primary analysis based on data from Angrisani et al,⁹ LRYGB dominated LAGB in 19.7% of simulations; for the analyses based on data from O'Brien et al,¹⁰ LRYGB dominated LAGB in virtually none of the simulations.

DISCUSSION

In this study, we used Markov modeling techniques to assess the cost-effectiveness of LAGB versus LRYGB, and both treatments versus no treatment, for managment of morbid obesity. Our model evaluated treatment-related weight loss and adverse events as predictors of quality-adjusted survival and cumulative costs. Cost-effectiveness was estimated in terms of cost per QALY gained and cost per life-year saved. In addition to deterministic sensitivity analyses, probabilistic analyses were performed to assess the effects of uncertainty in the analysis.

Our base-case analyses, which used estimates of treatment effectiveness from a prospective randomized trial of LAGB versus LRYGB,9 showed both LAGB and LRYGB to be cost-effective compared with no treatment. The ICERs for LAGB versus no treatment ($5400 per QALY gained) and for LRYGB versus no treatment ($5600 per QALY gained) are approximately equivalent. The estimated ICER for LRYGB compared with LAGB also was favorable at $6200 per QALY gained. The ICERs for LAGB versus no treatment, LRYGB versus no treatment, and LRYGB versus LAGB always decreased with initial patient BMI and generally decreased with female sex. The results of our study are consistent with those of previous studies in the literature that show cost-effectiveness for bariatric surgery compared with no treatment.^26-28 These results also compare favorably with other cost-effectiveness studies of major surgeries for chronic conditions, including coronary artery bypass grafting for treatment of angina.²⁹

High-quality comparative data on the relative effectiveness of LAGB and LRYGB in the medium to long term are lacking in the literature. Analyses using alternative estimates of efficacy based on a systematic literature review11 also demonstrate cost-effectiveness of LAGB and LRYGB versus no treatment. Compared with the Angrisani et al study,⁹ this study reports waning effectiveness of LRYGB after 3 years, resulting in a smaller gap in cumulative weight loss between LRYGB or LAGB after 5 years that was assumed to continue for the remainder of the model. In these analyses, estimated ICERs for LRYGB compared with LAGB were significantly larger than those in the base case (more than $100,000 per QALY in individuals with a BMI >40 kg/m²).

Deterministic and probabilistic sensitivity analyses show the cost-effectiveness results to be relatively robust to variations in key assumptions. Key drivers for the cost-effectiveness results included the initial procedure costs, costs of follow-up, and costs of severe adverse events. However, the tenor of the primary result—that LAGB and LRYGB have comparable and attractive ICERs compared with no treatment&mdash;remains the same.

It is important to note that the estimated cost offsets for this analysis were based on the average health expenditures, by BMI, in the general obese population. These estimates were likely to have underestimated the BMI-specific health expenditures in the treatment-seeking population. If this is the case, then we underestimated the cost offsets, and therefore overestimated the ICERs for bariatric surgery versus no treatment (ie, underestimated the incremental cost-effectiveness of bariatric surgery). This bias likely was offset by the fact that formerly morbidly obese individuals are likely to have higher medical costs than persons who have never been morbidly obese. We note that in a matched cohort analysis of commercially insured employed patients who sought and received bariatric surgery, costs of laparoscopic bariatric surgery (an average of $17,000 in 2005 dollars) were recouped by the payer in less than 3 years.³⁰

An additional limitation is the lack of data from comprehensive studies of the incidence of adverse events associated with LAGB and LRYGB in the medium to long term; we relied on the input of clinical experts to specify the decrease in adverse event rates over time. Moreover, adverse event rates vary across surgeons and are significantly lower for procedures performed in bariatric surgery centers of excellence.³¹ We investigated the importance of this assumption using 2-way sensitivity analyses, which showed our initial findings to be robust. Second, specific data on individuals with extremely high initial BMI are lacking in the literature. We used simple linear extrapolation to estimate parameters for the morbidly obese II and super obese groups based on trends for lower BMI categories. To the extent that linear extrapolations are likely to underestimate the mortality risks and health expenditures associated with these individuals, we are likely to have overestimated the ICERs for (underestimated the cost-effectiveness of) LAGB and LRYGB versus no treatment, and potentially for LRYGB versus LAGB. Finally, we also note that due to data limitations, we were not able to evaluate newer techniques for morbid obesity such as the gastric sleeve and intragastric balloon; assessment of these techniques should be undertaken as data become available.

Results of our analyses lead us to conclude that both LAGB and LRYGB provide significant weight loss and are costeffective at conventionally accepted thresholds for medical interventions compared with no treatment. This conclusion is supported by our use of relatively conservative assumptions and sensitivity analysis. The cost-effectiveness estimates of LRYGB versus LAGB are extremely sensitive to model assumptions. Our base-case analysis includes a 1-time utility decrement associated with the initial procedure. Alternative analyses may consider long-term increases in utility from intangible benefits of LAGB not related to weight loss, such as peace of mind due to reversibility or fewer dietary restrictions. Using threshold analyses, we find that under base-case assumptions, overall utility is equivalent for the treatments only if LAGB is associated with a relatively high ongoing incremental utility benefit of 0.11 over the first 10 years. In contrast, if we use estimates from O'Brien et al,10 patients would only need to assign LAGB an incremental utility weight of 0.02 over the first 10 years to receive equivalent benefit from LAGB and LRGBY.

This sensitivity of the incremental cost-effectiveness of LRYGB versus LAGB underscores the need for long-term, high-quality comparative studies to be performed in this field. At this time, decisions between the 2 procedures can be based on other factors such as patient or provider preference.

Author Affiliations: From i3 Innovus (JC, LJM), Medford, MA; Tufts Medical Center (SAS), Boston, MA; Allergan, Inc (BCH, JTL); and Harvard School of Public Health (MCW), Boston, MA.

Funding Source: This study was funded by Allergan, Inc. Author Disclosures: Dr Campbell and Ms McGarry are employees of i3 Innovus, which was commissioned by Allergan, Inc, to conduct this research. Dr Shikora reports receiving payment from i3 Innovus for his involvement in the preparation of this manuscript. He also reports serving as a paid advisor for Allergan, Coviden, and Ethicon. Mr Hale and Dr Lee are employees of Allergan, Inc, a manufacturer of a lap band. Dr. Weinstein reports serving as a paid consultant to i3 Innovus for his involvement in this study.

Authorship Information: Concept and design (JC, LJM, SAS, BCH, JTL, MCW); acquisition of data (SAS); analysis and interpretation of data (JC, LJM, MCW); drafting of the manuscript (JC, SAS); critical revision of the manuscript for important intellectual content (JC, LJM, SAS, BCH, JTL, MCW); statistical analysis (JC, MCW); obtaining funding (JTL); administrative, technical, or logistic support (BCH, JTL); and supervision (LJ M, JTL, MCW).

Address correspondence to: Joanna Campbell, PhD, 10 Cabot Rd, Ste 304, Medford, MA 02155. E-mail: joanna.campbell@i3innovus.com.

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