Thymectomy Plus Prednisone Shows Benefit in Patients With Nonthymomatous Myasthenia Gravis

Five-year results from the extended randomized MGTX trial demonstrated that the addition of thymectomy to prednisone leads to long-lasting lower quantitative myasthenia gravis (QMG) scores and prednisone dosing.

Performing thymectomy in patients with nonthymomatous myasthenia gravis has remained controversial since the practice guideline in 2000 could not conclusively determine a benefit from the procedure. Since then, many of the authors of the practice guideline have been calling for a randomized controlled trial to adequately address this issue.

In 2006, investigators in the MGTX trial began to enroll patients with nonthymomatous myasthenia gravis and randomized them to receive either prednisone with thymectomy or prednisone alone. At the 3-year timepoint, patients who underwent thymectomy had superior improvements in myasthenic weakness and required lower corticosteroid requirements than patients only on prednisone. In a recent study, investigators report the results of the extension study for the MGTX trial to determine if the benefits continued past 3 years.

Patients were enrolled in the extension study if they completed the initial 36 months of MGTX. A total of 33 patients in the prednisone alone group and 35 patients in the thymectomy plus placebo group chose to participate. Among them, 26 patients in the thymectomy plus prednisone group and 24 patients in the prednisone alone group completed the 60-month visit.

At 60 months, patients in the thymectomy and prednisone group had significantly improved time-weighted mean QMG scores from month 0 to 60 compared with patients who only received prednisone (5.47 vs 0.34; P = .0007). Mean alternate-day prednisone doses were also significantly lower in the thymectomy group than the prednisone alone group (24 mg vs 48 mg; P = .0002). Benefits were seen across all subgroups, except for the analysis in men only, which did not show a significant difference in prednisone doses. Patients who were prednisone-naïve also did not have significantly different time-weighted mean QMG scores between the two groups.

Cumulative days spent in the hospital for myasthenia gravis exacerbations were similar between the 2 groups. However, the number of hospitalizations from nervous system disorders was much higher in the prednisone alone group compared with the thymectomy with prednisone group. Patients requiring azathioprine or intravenous immunoglobulin was also significantly lower in the thymectomy group versus the prednisone alone group. For the 2 additional years of observation, only 2 patients from each group had an increase of 2 points in QMG score. No deaths occurred during this extension period.

Based on the persisting thymectomy benefits over 5 years, investigators concluded that thymectomy should be favored in patients with nonthymomatous myasthenia gravis.

Reference

Wolfe GI, Kaminski HJ, Aban IB, et al. Long-term effect of thymectomy plus prednisone versus prednisone alone in patients with non-thymomatous myasthenia gravis: 2 -year extension of the MGTX randomized trial [published online January 25, 2019]. Lancet Neurol. doi: 10.1016/S1474-4422(18)30392-2.