胸腺腫非合併重症筋無力症における拡大胸腺摘除術の意義—MGTX study

The Significance of Extended Thymectomy in Non-Thymomatous Myasthenia Gravis: an MGTX Study

2016年8月に，胸腺腫を合併しない重症筋無力症（MG）に対する拡大胸腺摘除術の安全性と有効性に関する国際ランダム化比較試験（MGTX study）の結果が公表された。ステロイド治療に拡大胸腺摘除術を併用すると，QMGスコアの軽減，ステロイド総投与量の減量，治療に伴う症状や副作用を抑えてQOL（quality of life）向上をもたらすことが明らかになった。今後，この結果を踏まえ，MGの標準的治療の再検討が必要である。

Abstract

In August 2016, the results of the international randomized, controlled, trial that studied the safety and efficacy of extended trans-sternal thymectomy (ETTX) for patients with non-thymomatous myasthenia gravis (MG) was published. The inclusion criteria for this study were: 1) male and female subjects aged＞18.0 and ＜60.0 years with non-thymomatous MG; 2) MG Foundation of America (MGFA) Clinical Classification Class II-IV at entry; 3) anti-acetylcholine receptor antibody (AChRAb) positive; and 4) receiving optimal oral anticholinesterase treatment with or without oral prednisone. Subjects were randomized to one of two protocols: prednisone alone or extended transsternal thymectomy (ETTX) plus prednisone. A total of 126 patients were randomized. The ETTX plus prednisone protocol improved the quantitative MG scores, decreased the total amount of prednisone, and decreased symptoms and side effects, resulting in a better quality of life compared with the prednisolone alone protocol. These results have required us to change our standard therapeutic protocol for MG. In addition, the safety and efficacy of ETTX with thymectomy via robotic methods needs to be considered. The MGTX study did not address the efficacy and safety of ETTX for younger or older patients, for MGFA Clinical Classification Class I or V patients, or for AChRAb-negative patients.