Does myasthenia gravis influence overall survival and cumulative incidence of recurrence in thymoma patients? A Retrospective clinicopathological multicentre analysis on 797 patients

OBJECTIVE: Aim of this study is to evaluate whether Myasthenia Gravis (MG) might influence Overall Survival (OS) and Cumulative Incidence of Recurrence (CIR) in thymoma patients. METHODS: this is a multicenter retrospective study of patients operated in 6 high-volume Italian Institutions between 1990 and 2012. OS was estimated by the Kaplan-Meier method and CIR by considering death from any cause as a competing event. Crude and adjusted comparisons by MG for OS and CIR were performed using Cox and Fine&Gray models. Adjusted models included MG, age, gender, stage, histology, induction therapy, completeness of resection, adjuvant therapy. RESULTS: Seven hundred ninety-seven patients were included: 375 (47%) had MG. MG patients were younger and more frequently female, with a B2-B3 thymoma. At the end of the study, 129 patients (54 with MG) developed a recurrence and 165 (66 with MG) died. At univariate analysis, MG showed a slight protective effect on OS, not confirmed by the multivariate model. Age, incomplete resection, advanced stages and thymic carcinoma were negative prognostic variables. Univariate analyses showed no evidence of MG protective effect on CIR. Advanced stages and induction therapy were significant negative predictors. CONCLUSION: our study showed that MG was significantly associated with female, lower age and B2-B3 thymoma; it demonstrated a slight protective effect on OS at the univariate analysis which was not confirmed in multivariate as well as no impact on CIR. Advanced tumor stages and thymic carcinoma histology for OS and induction therapy and advanced stages for CIR were negative prognostic variables.