Predictors of post-thymectomy long-term neurological remission in thymomatous myasthenia gravis: an analysis from a multi-institutional database.

OBJECTIVES: Thymectomy is the treatment of choice for thymomatous myasthenia gravis (MG) for both oncological and neurological aspects. However, only a few studies comprising small numbers of patients have investigated post-thymectomy neurological outcomes. We examined post-thymectomy long-term neurological outcomes and predictors of thymomatous MG using a multi-institutional database. METHODS: In total, 193 patients (47.3 +/- 12.0 years; male:female = 90:103) with surgically resected thymomatous MG between 2000 and 2013 were included. Complete stable remission (CSR) and composite neurological remission (CNR), defined as the achievement of CSR and pharmacological remission after thymectomy, were evaluated. Predictors for CSR and CNR were examined by Cox regression analysis. RESULTS: The median duration between MG and thymectomy was 3.1 months. In addition, 161 patients (83.4%) had symptoms less than Myasthenia Gravis Foundation of America clinical classification III. All patients underwent an extended thymectomy; there were no perioperative deaths. The 10-year cumulative probability of CSR and CNR was 36.9% and 69.1%, respectively. Mild preoperative symptoms were a significant predictor for CSR (P = 0.040), and a large tumour was a predictor for CNR (P<0.001). Patients with a large tumour were associated with early MG onset and no steroid treatment. Surgical methods, thymoma stage and histological subtypes were not associated with long-term neurological remission. CONCLUSIONS: Large tumour size and preoperative mild symptoms were predictors for long-term neurological outcome in thymomatous MG. Considering that patients with early onset of MG and no immunosuppressive treatment tend to have large tumours, early surgical intervention for patients with thymomatous MG having mild symptoms might be beneficial for controlling neurological outcomes.