Economic Evaluation of Thymectomy for the Treatment of Nonthymomatous Myasthenia Gravis.

Importance: Myasthenia gravis (MG) is a chronic autoimmune disease that significantly impairs patients' quality of life by causing fluctuating muscle weakness and fatigue. While pharmacological treatment with corticosteroids remains a cornerstone of treatment, long-term use is often associated with substantial adverse effects. Although thymectomy is an established and effective alternative and adjunct to pharmacological treatment, its long-term cost-effectiveness within the UK National Health Service (NHS) is unknown. Objective: To evaluate the cost-effectiveness of thymectomy in addition to prednisolone therapy compared with prednisolone therapy alone for patients with nonthymomatous MG. Design, Setting, and Participants: This economic evaluation used a Markov state-transition model to simulate the costs and health outcomes of patients with nonthymomatous MG. The patients' baseline characteristics, disease progression, and treatment efficacy were derived from patient-level data from the Thymectomy Trial in Nonthymomatous Myasthenia Gravis Patients Receiving Prednisone Therapy (MGTX) clinical trial. The model adopted a UK NHS and Personal Social Services perspective over a lifetime horizon. Data analysis was performed from June 2024 to October 2025. Main Outcomes and Measures: The primary outcomes were incremental costs and quality-adjusted life years (QALYs) discounted at 3.5% per annum and the incremental cost-effectiveness ratio (ICER). Extensive deterministic and probabilistic sensitivity analyses were conducted to assess the robustness of the findings to parameter uncertainty. Results: There were 126 participants in the MGTX trial, with a mean age of 35.08 years; 70.63% were female. In the base-case analysis, thymectomy plus prednisolone dominated prednisolone alone, yielding higher health gains (14.63 QALYs vs 14.11 QALYs) and lower lifetime costs (£181 716 vs £194 730). This generated an incremental gain of 0.52 QALYs and a cost saving of £13 014 per patient. The results were robust across a wide range of sensitivity analyses. Probabilistic analysis (1000 simulations) showed that thymectomy had a greater than 99% probability of being cost-effective at a willingness-to-pay threshold of £25 000 per QALY. Conclusions and Relevance: In this economic evaluation, thymectomy was found to be a highly cost-effective intervention for nonthymomatous MG in the UK and likely to be cost-saving relative to prednisolone alone. These findings support current clinical guidelines recommending thymectomy for eligible patients and establish it as the most relevant comparator in evaluations of future health technologies. More broadly, this study demonstrates the importance of high-quality randomized clinical trial evidence in enabling health technology assessment of surgical procedures.