Trends in thymectomy for myasthenia gravis in Japan: analysis of a nationwide surgical registry from 1996 to 2023.

BACKGROUND: Thymectomy for generalized myasthenia gravis (MG) without thymoma and with anti-acetylcholine receptor antibody gained evidence-based support following the publication of the MGTX study in 2016, demonstrating its therapeutic efficacy. Consequently, the number of thymectomies increased in the United States. Trends in thymectomy for this condition in Japan is investigated. METHODS: Thymectomy reported in The Japanese Association for Thoracic Surgery (JATS) Annual Report from 1996 to 2023 was analyzed. Annual numbers of thymectomies were reviewed according to surgical approach, non-thymomatous MG, thymomatous MG, and operative mortality. RESULTS: A total of 91,087 thymic surgeries were reported from 693 certified institutions. The annual number of thymectomies for MG remained stable. Thymectomy for thymomatous MG increased from 182 cases in 1996 to 380 in 2023, whereas that for non-thymomatous MG declined from its peak of 375 cases in 2001 to 97 in 2023. Overall postoperative hospital mortality of non-thymomatous MG was 0.26%. Thymectomy for thymoma, in contrast, markedly increased from 812 cases in 1996 to 2210 in 2023. The proportion of minimally invasive procedures (VATS/RATS) gradually increased. CONCLUSIONS: Opposing trends were observed: a decline in thymectomy for non-thymomatous MG, an increase in thymoma resection, and widespread adoption of minimally invasive procedures with excellent safety. The optional status of thymectomy in Japanese MG guidelines may contribute to this pattern. Considering the long-term symptom relief achieved by surgery and the high ongoing cost of biologic drugs, thymectomy remains a rational therapeutic option. Future treatment strategies should integrate surgical safety with long-term economic perspectives.