Thymectomy improves clinical outcomes for myasthenia gravis




Thymectomy improved 3-year clinical outcomes and proved superior to medical therapy for mild to severe nonthymomatous myasthenia gravis, according to a report published online Aug. 11 in the New England Journal of Medicine.

Compared with standard prednisone therapy, thymectomy plus prednisone decreased the number and severity of symptoms, allowed the lowering of steroid doses, decreased the number and length of hospitalizations for disease exacerbations, reduced the need for immunosuppressive agents, and improved health-related quality of life in an international, randomized clinical trial, said Gil I. Wolfe, MD, of the department of neurology, State University of New York at Buffalo and his associates.

Until now, thymectomy was known to be beneficial in some cases of myasthenia gravis “but with widely varying rates of clinical improvement or remission.” And the success of immunotherapy has raised the question of whether an invasive surgery is necessary. Data from randomized, controlled studies have been sparse.

Moreover, thymectomy rarely causes adverse effects, but “the procedure can cost up to $80,000 and can be associated with operative complications that need to be weighed against benefits.” In comparison, medical therapy with glucocorticoids and other immunosuppressive agents is less invasive but is definitely associated with adverse events, including some that are life threatening, and negatively impacts quality of life, the investigators said.

To address the lack of randomized controlled trial data, they assessed 3-year outcomes in 126 patients treated at 67 medical centers in 18 countries during a 6-year period. The study participants were aged 18-65 years, had a disease duration of less than 5 years at enrollment (median duration, 1 year), and had class II (mild generalized disease) to class IV (severe generalized disease) myasthenia gravis. These patients were randomly assigned to undergo thymectomy and receive standard prednisone therapy (66 participants) or to receive standard prednisone alone (60 participants).

Thymectomy was performed using a median sternotomy “with the goal of an en bloc resection of all mediastinal tissue that could anatomically contain gross or microscopic thymus.”

At follow-up, time-weighted average scores on the Quantitative Myasthenia Gravis scale were significantly lower by 2.85 points, indicating improved clinical status, in the thymectomy group than in the control group. Time-weighted average prednisone dose also was significantly lower, at an average alternate-day dose of 44 mg in the thymectomy group and 60 mg in the control group, Dr. Wolfe and his associates said (N Engl J Med. 2016 Aug 11. doi: 10.1056/NEJMoa1602489).

On a measure of treatment-related complications, scores favored thymectomy with regard to the number of patients with symptoms, the total number of symptoms, and the distress level related to symptoms throughout the study period. Fewer patients in the thymectomy group required hospitalization for exacerbations of myasthenia gravis (9% vs. 37%), and the mean cumulative number of hospital days was lower with thymectomy (8.4 vs. 19.2).

In addition, scores on the Myasthenia Gravis Activities of Daily Living scale favored thymectomy (2.24 vs. 3.41). Fewer patients in the thymectomy group required azathioprine (17% vs. 0.48%). And the percentage of patients who reported having minimal manifestations of the disease at 3 years was significantly higher with thymectomy (67%) than with prednisone alone (47%).

This study was supported by the National Institute of Neurological Disorders and Stroke, the Muscular Dystrophy Association, and the Myasthenia Gravis Foundation of America and received no commercial support. Dr. Wolfe reported ties to Alexion Pharmaceuticals, Alpha Cancer Technologies, Argenx, Baxalta, CSL Behring, Grifols, and UCB, and his associates reported ties to numerous industry sources.

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