Research in context
Evidence before this study
We searched PubMed with the terms “randomised”, “thymectomy”, and “myasthenia gravis” to identify articles published in English between Jan 1, 2012, and Aug 28, 2018. This search overlapped with previous searches done during the design, conduct, and publication stages of the international, multicentre, randomised controlled, rater-blinded Thymectomy Trial in Non-Thymomatous Myasthenia Gravis Patients Receiving Prednisone (MGTX). Our search identified one publication of the results of MGTX and one publication from our investigator group reporting biomarker results from the trial. We also identified six letters to the editor or editorials commenting on the MGTX results. No other randomised studies of thymectomy in patients with myasthenia gravis were identified. Before MGTX, the results of observational studies mostly suggested that thymectomy improved outcomes in patients with non-thymomatous myasthenia gravis. Practice guidelines, however, identified several flaws in these studies (including confounding variables of age, sex, and disease severity), showing the need for a randomised controlled trial. The results of MGTX showed that extended transsternal thymectomy combined with a standardised prednisone protocol was superior to prednisone alone at 3 years in improving clinical status and lowering medication requirements in patients with generalised non-thymomatous myasthenia gravis.
Added value of this study
The MGTX extension study, in which patients were followed up under the same protocol until month 60 (5 years) showed that thymectomy plus prednisone treatment continued to confer benefits—including improved disease outcomes, reduced prednisone requirements, and fewer hospitalisations for disease exacerbations—compared with prednisone alone in patients with generalised non-thymomatous myasthenia gravis. Additionally, the extension study results for the thymectomy plus prednisone group are favourable compared with those for other observational long-term outcome studies in patients with myasthenia gravis that tracked minimal manifestation status.
Implications of all the available evidence
Thymectomy within the first few years of the disease course in addition to prednisone therapy confers benefits that persist for 5 years compared with prednisone alone in patients with generalised non-thymomatous myasthenia gravis. Results from the extension study provide further support for the use of thymectomy in management of myasthenia gravis and should encourage serious consideration of this treatment option in discussions between clinicians and their patients.