The first reported use of thymectomy in patients with non-thymomatous myasthenia gravis (MG) was 75 years ago. Of six patients who underwent surgery, three had a favourable response. Subsequent retrospective studies have shown benefits of thymectomy in patients with non-thymomatous MG but with widely varying rates of clinical improvement or remission. Despite calls for a randomized, controlled study, data are lacking and uncertainty persists regarding the benefit of thymectomy and the clinical characteristics of the patients who should be offered the procedure.
Medical therapy with Glucocorticoids and other immunosuppressive agents place patients at risk for adverse events, some of which are life-threatening and affect quality of life. Therefore, establishing the role of thymectomy in patients receiving glucocorticoids to manage myasthenia gravis would guide decisions regarding treatment and the costs of healthcare.
A trial, called the Thymectomy Trial in Non-Thymomatous Myasthenia Gravis Patients Receiving Prednisone Therapy (MGTX), was conducted recently. It was an international, randomized, single-blind (rater-blinded) trial to determine whether extended transsternal thymectomy combined with a standardized prednisone protocol would be superior to prednisone alone after three years, with respect to lessening myasthenic weakness, lowering the total dose of prednisone, and enhancing quality of life. Extended transsternal thymectomy was chosen because it provides reproducible resection of the maximal amount of thymic tissue with low morbidity and a limited risk of phrenic-nerve injury.
The trial leaders were from USA and UK but it encompassed five continents including Asia. The trial enrolled 126 subjects with MG and randomly assigned them to thymectomy plus alternate-day prednisone or alternate-day prednisone alone. Over a three-year period, thymectomy improved multiple clinical outcomes, including quantitative strength testing, average alternating-day prednisone requirements (44 versus 60 mg), need for azathioprine immunosuppression (17 versus 48 percent), and hospitalization for acute exacerbations (9 versus 37 percent).
In conclusion, this randomized, medication-controlled, rater-blinded trial showed a benefit of thymectomy in patients with myasthenia gravis over a period of three years with respect to clinical outcomes, requirements for prednisone and azathioprine therapy, the number of symptoms and the distress level related to immunosuppressive agents, and the need for hospitalization to manage disease exacerbations.
Based on these results and prior observational data, it can now be recommended that thymectomy for patients aged less than 60 years with non-thymomatous, generalized acetylcholine receptor (AChR) antibody-associated MG is preferable to medical therapy alone.
Of course, in patients with thymoma – with or without MG – thymectomy is the procedure of choice if resection is feasible.
The author of this article, Dr Harinder Singh Bedi, is head of the cardiovascular, endovascular and thoracic surgery department at the Christian Medical College and Hospital, Ludhiana, Punjab.