[S36.004] Thymectomy For Non-Thymomatous Myasthenia Gravis: A Propensity Score Matched Study.

Carolina Barnett Tapia, Hans Katzberg, Shaf Keshavjee, Vera Bril
Toronto, ON, Canada


Objective: To study the efficacy of thymectomy in achieving Remission or Minimal manifestation status in patients with non-thymomatous, generalized Myasthenia Gravis (MG).
Background: The efficacy of thymectomy in patients with non-thymomatous MG is still unclear. Most studies have been limited due to no adjustment for confounders (e.g immunosuppressants), unclear definitions of remission and lack of control group. A randomized study is underway, but its results are not available yet.
Methods: Patients with generalized MG and minimum follow-up of 6 months were included. Demographic data at onset, and treatments were recorded, as well as the MGFA post-intervention status at the last visit. Bayesian propensity score (PS) models were used to achieve a matched cohort of treated and untreated patients, balanced by age, sex, disease duration, severity at diagnosis and use of immunosuppressants. AChRAb status was excluded as not available in all patients. Cox proportional models were built to study treatment effects to achieve remission or minimal manifestation (Remission-MM) status.
Results: 395 patients were identified. 183(46%) had a thymectomy. Thymectomy patients were younger (34.8 vs. 63.4 years, p<0.001), with more females (67.8% vs 41.9%, p<0.001) and more patients in MGFA classes 4&5 (21.8% vs 12.7%, p=0.01). A matched cohort (n=102) was created. The adjusted hazard ratio (HR) for the matched cohort was 1.43 (CI:1.32-1.54), and 1.51 (CI:0.8-2.84) for the unmatched cohort. The predicted Remission-MM rate was 16.6% in treated and 10.2% in controls at 5 years and 25.8% vs. 16.6% at 7 years. A Bayesian Cox model for the matched cohort had an estimated probability of efficacy (HR>1) of 96%.
Discussion: In this cohort, thymectomy was associated with a higher probability of achieving Remission-MM status through time, controlling for several confounders. These results might not be applicable to a population radically different in age, severity or medications from the matched cohort.
Category - Neuromuscular and Clinical Neurophysiology (EMG): Neuromuscular Junction Diseases

Wednesday, April 30, 2014 4:30 PM

S36: Platform Blitz: Neuromuscular Disease: Clinical (4:00 PM-5:45 PM)

 

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