Outcomes after thymectomy in non-thymomatous myasthenia gravis

Background: Guidelines by the myasthenia gravis (MG) Foundation of America suggest patients aged 18 to 50 years with non-thymomatous myasthenia gravis (NTMG) benefit from thymectomy. Our objective was to investigate utilization of thymectomy in NTMG patients outside the confines of a clinical trial. Methods: From the Optum de-identified Clinformatics Data Mart Claims Database (2007 to 2021), we identified patients diagnosed with MG between 18-50 years old. We then selected patients who received a thymectomy within 12 months of MG diagnosis. Outcomes included use of steroids, non-steroidal immunosuppressive agents (NSIS), and rescue therapy (plasmapheresis or intravenous immunoglobulin), as well as NTMG-related emergency department (ED) visits and hospital admissions. These outcomes were compared in the 6-months before and after thymectomy. Results: A total of 1,298 patients met our inclusion criteria, of whom 45 (3.47%) received a thymectomy, performed via minimally invasive surgery in 53.3% of cases (n=24). In comparing the pre- to post-operative period, we noted that steroid use increased (53.33% to 66.67%, P=0.034), NSIS use remained stable, and use of rescue therapy decreased (44.44% to 24.44%, P=0.007). Costs associated with steroid and NSIS use remained stable. However, the mean costs of rescue therapy decreased (from $13,243.98 to $8,486.26, P=0.035). Hospital admissions and ED visits related to NTMG remained stable. There were 2 readmissions within 90 days (4.44%) associated with thymectomy. Conclusions: Patients with NTMG undergoing thymectomy experienced less need for rescue therapy following resection, albeit with increased rates of steroid prescriptions. Thymectomy is infrequently performed in this patient population despite acceptable postsurgical outcomes.