Preoperative Myasthenia Gravis and Five-Year Outcomes After Thymoma Resection: A Multicenter Cohort Study

The prognostic association of preoperative myasthenia gravis (MG) with outcomes after thymoma resection remains uncertain.

This three-center cohort included 1,368 patients undergoing thymoma resection (2009-2025); MG status was fixed at surgery. We evaluated overall survival and, after R0 resection, documented recurrence with death as a competing event. Stabilized weights adjusted for center, age, sex, histology, Masaoka-Koga stage, tumor diameter, and surgery year. Alternative analyses addressed recorded-M0 disease, detailed balance, operative extent, and follow-up.

Myasthenia gravis was present in 257 patients (18.8%). Adjusted 5-year overall survival was 87.3% with MG and 97.3% without MG, an all-cause mortality-risk difference of 10 percentage points (95% confidence interval [CI] 5.2-15.1). Among 1,254 R0 resections, adjusted recurrence was 10% with MG and 2% without MG (difference, 8.0 points; 95% CI 3.2-13.3). After excluding 65 recorded M1a cases, mortality and recurrence differences were 8.6 points (95% CI 3.8-14.1; 28 deaths) and 7.6 points (95% CI 2.7-13.1; 17 recurrences). Detailed-category weighting yielded differences of 10.4 and 8.2 points; surgical and follow-up analyses were directionally consistent.

Preoperative MG was associated with higher adjusted 5-year all-cause mortality and documented recurrence after R0 resection. Similar directions after excluding recorded M1a disease suggest that known pleural dissemination was not the sole explanation. These prognostic associations do not establish causality, and the survival difference cannot be attributed specifically to thymoma progression.