Cost-Utility Analysis of Mycophenolate Mofetil versus Azathioprine Based Regimens for Maintenance Therapy of Proliferative Lupus Nephritis

Abstract

Background/Aims. We aimed to examine the cost-effectiveness of mycophenolate mofetil (MMF) and azathioprine (AZA) as maintenance therapy for patients with Class III and Class IV lupus nephritis (LN), from a United States (US) perspective. Methods. Using a Markov model, we conducted a cost-utility analysis from a societal perspective over a lifetime horizon. The modeled population comprised patients with proliferative LN who received maintenance therapy with MMF (2 gm/day) versus AZA (150 mg/day) for 3 years. Risk estimates of clinical events were based on a Cochrane meta-analysis while costs and utilities were retrieved from other published sources. Outcome measures included costs, quality-adjusted life-years (QALY), incremental cost-effectiveness ratios (ICER), and net monetary benefit. Results. The base-case model showed that, compared with AZA strategy, the ICER for MMF was $2,630,592/QALY at 3 years. Over the patients' lifetime, however, the ICER of MMF compared to AZA was $6,454/QALY. Overall, the ICER results from various sensitivity and subgroup analyses did not alter the conclusions of the model simulation. Conclusions. In the short term, an AZA-based regimen confers greater value than MMF for the maintenance therapy of proliferative LN. From a lifelong perspective, however, MMF is cost-effective compared to AZA.

Figure 1

(a) Markov state transition diagram illustrating the health states and transitions for each treatment strategy for the initial 3 years. The lifetime model consists of the initial 3-year period of maintenance therapy followed by a posttreatment phase as shown in (b). (b) Markov state transition diagram illustrating the health states and transitions for each treatment strategy for the posttreatment phase (after 3 years). LN: lupus nephritis; AZA: azathioprine; MMF: mycophenolate mofetil; IV CYC: intravenous cyclophosphamide; ESRD: end stage renal disease.

Figure 2

Tornado diagram of the 3-year base-case model, demonstrating one-way sensitivity analysis of each variable in the model. Each bar represents a range of expected values (EV), expressed as net monetary benefit in US dollars, over plausible estimates for an individual variable. The dotted vertical line indicates the base-case expected value. WTP: willingness-to-pay.

Figure 3

Incremental cost-effectiveness scatter plots of the base-case model. (a) 3 years; (b) 10 years after completing 3-year maintenance therapy; (c) 40 years after completing 3-year maintenance therapy. Each single point represents pairs of incremental cost and effectiveness values from probabilistic sensitivity analyses via second-order Monte Carlo simulation of 1,000 iterations. The ellipsis represents the 95% confidence interval. The dotted diagonal line represents the WTP threshold of $50,000/QALY. AZA: azathioprine; MMF: mycophenolate mofetil; WTP: willingness-to-pay; QALY: quality-adjusted life-years.