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Risk factors for developing post‐thymectomy myasthenia gravis in patients with thymoma
Author(s) -
Kim Ahwon,
Choi SeokJin,
Kang Chang Hyun,
Lee Seonkyung,
Son Hyoshin,
Kim JinAh,
Shin JeYoung,
Kim SungMin,
Hong YoonHo,
Sung JungJoon
Publication year - 2021
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.27169
Subject(s) - thymectomy , thymoma , myasthenia gravis , medicine , hazard ratio , surgery , gastroenterology , confidence interval
Background Thymectomy is required for the treatment of thymoma‐associated myasthenia gravis (MG). However, MG may develop only after thymectomy, a condition known as post‐thymectomy MG. This study aimed to investigate the risk factors for post‐thymectomy MG in patients with thymoma. Methods We retrospectively identified 235 patients with thymoma who underwent thymectomy at a single hospital from January 2008 to December 2017: 44 with preoperatively diagnosed MG were excluded, leaving 191 patients in the final analysis. Univariable survival analyses using Cox proportional hazards regression model and Kaplan‐Meier estimate were conducted to identify risk factors for post‐thymectomy MG. Results Post‐thymectomy MG developed in 4.2% (8/191) of the patients with thymoma between 18 days and 108 mo after surgery. Hazard ratios (HRs) of pre‐ and postoperative anti‐acetylcholine receptor antibody (AChR‐Ab) titers were 2.267 ( P = .002) and 1.506 ( P < .001), respectively. Patients with extended thymectomy had a low chance of post‐thymectomy MG (HR 0.035, P = .007). Larger thymoma (HR, 1.359; P = .005) and type A or AB thymoma according to World Health Organization histological classification (HR, 11.92; P = .021) were associated with higher chances of post‐thymectomy MG. Within the subgroup of preoperatively AChR‐Ab seropositive patients, post‐thymectomy MG developed in 22.2% (6/27). Conclusions Pre‐ and postoperative AChR‐Ab levels should be measured in patients with thymoma. A large thymoma and partial thymectomy appear to be associated with a higher probability of post‐thymectomy MG.