Literature Review

Clinical benefits persist 5 years after thymectomy for myasthenia gravis



Thymectomy may continue to benefit patients with myasthenia gravis 5 years after the procedure, according to an extension study published in Lancet Neurology. Patients with generalized nonthymomatous myasthenia gravis who underwent thymectomy had better long-term clinical outcomes and required less prednisone, compared with patients who received prednisone alone.

Gil I. Wolfe, MD, chair of the department of neurology at the University at Buffalo in New York Douglas Levere/University at Buffalo

Dr. Gil I. Wolfe

The study evaluated the clinical status, medication requirements, and adverse events of patients with myasthenia gravis who completed a randomized controlled trial of thymectomy plus prednisone versus prednisone alone and agreed to participate in a rater-blinded 2-year extension.

“Thymectomy within the first few years of the disease course in addition to prednisone therapy confers benefits that persist for 5 years ... in patients with generalized nonthymomatous myasthenia gravis,” said lead study author Gil I. Wolfe, MD, chair of the department of neurology at the University at Buffalo in New York, and his research colleagues. “Results from the extension study provide further support for the use of thymectomy in management of myasthenia gravis and should encourage serious consideration of this treatment option in discussions between clinicians and their patients,” they wrote. “Our results should lead to revision of clinical guidelines in favor of thymectomy and could potentially reverse downward trends in the use of thymectomy in overall management of myasthenia gravis.”

The main 3-year results of the Thymectomy Trial in Nonthymomatous Myasthenia Gravis Patients Receiving Prednisone (MGTX) were reported in 2016; the international trial found that thymectomy plus prednisone was superior to prednisone alone at 3 years (N Engl J Med. 2016 Aug 11;375[6]:511-22). The extension study aimed to assess the durability of the treatment response.

MGTX enrolled patients aged 18-65 years who had generalized nonthymomatous myasthenia gravis of less than 5 years’ duration and Myasthenia Gravis Foundation of America Clinical Classification Class II-IV disease. Of 111 patients who completed MGTX, 68 entered the extension study, and 50 completed the 60-month assessment (24 patients in the prednisone alone group and 26 patients in the prednisone plus thymectomy group).

At 5 years, patients in the thymectomy plus prednisone group had significantly lower time-weighted average Quantitative Myasthenia Gravis (QMG) scores (5.47 vs. 9.34) and mean alternate-day prednisone doses (24 mg vs. 48 mg), compared with patients who received prednisone alone. Twelve of 35 patients in the thymectomy group and 14 of 33 patients in the prednisone group had at least one adverse event by month 60. No treatment-related deaths occurred in the extension phase.

At 5 years, significantly more patients who underwent thymectomy had minimal manifestation status (i.e., no functional limitations from the disease other than some muscle weakness) – 88% versus 58%. The corresponding figures at 3 years were 67% and 47%.

In addition, 3-year and 5-year data indicate that the need for hospitalization is reduced after surgery, compared with medical therapy alone, Dr. Wolfe said.

Two patients in each treatment arm had an increase of 2 points or more in the QMG score, indicating clinical worsening.

“Our current findings reinforce the benefit of thymectomy seen in [MGTX], dispelling doubts about the procedure’s benefits and how long those benefits last,” said Dr. Wolfe. “We do hope that the new findings help reverse the apparent reluctance to do thymectomy and that the proportion of patients with myasthenia gravis who undergo thymectomy will increase.”

The authors noted that the small sample size of the extension study may limit its generalizability.

The study received funding from the National Institutes of Health. Dr. Wolfe reported grants from the NIH, the Muscular Dystrophy Association, the Myasthenia Gravis Foundation of America, CSL-Behring, and ArgenX, as well as personal fees from Grifols, Shire, and Alexion Pharmaceuticals. Coauthors reported working with and receiving funds from agencies, foundations, and pharmaceutical companies.

SOURCE: Wolfe GI et al. Lancet Neurol. 2019 Jan 25. doi: 10.1016/S1474-4422(18)30392-2.

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