The effectiveness of thymectomy as a cure for myasthenia gravis has long been debated, but the publication of Myasthenia Gravis Thymectomy Treatment (MGTX) trial results, showing that thymectomy improved outcomes over 3 years in patients with nonthymomatous myasthenia gravis, has gone a long way toward settling the debate, Joshua R. Sonett, MD, and his coauthors noted in a feature expert opinion (J Thorac Cardiovasc Surg. 2017;154:306-9).
The MGTX trial randomized patients with nonthymomatous MG into two treatment groups: medical therapy alone or thymectomy with medical therapy (N Engl J Med. 2016;375:511-22). For uniformity, the study mandated one type of thymectomy, an extended transsternal approach. The study was 12 years in the making, with 6 years of patient accrual followed by 3 years of surveillance, Dr. Sonett and his coauthors noted.
Dr. Joshua R. Sonett
Those markers include an average quantitative myasthenia score of 6.15 for the thymectomy group vs. 8.99 for the medical therapy group (P less than .0001); a lower dose of prednisone to attain improved neurologic status (44 mg vs. 60 mg; P less than .001); time-weighted average score on the Myasthenia Gravis Activities of Daily Living scale (2.24 vs. 3.41; P = .008); azathioprine use (17% vs. 48%; P less than .001); percentage of patients who had minimal-manifestation status at month 36 (67% vs. 47%; P = .03); and hospitalization for myasthenia-related symptoms (9% vs. 37%). “Interestingly,” the researchers wrote, “despite these quantitative results, no difference was seen in the quality of life measured surveys.”
An ancillary study, Bio-MGTX, was performed simultaneously to investigate pathologic and serum markers. “Many questions still need to be answered in regard to the role of thymectomy in MG,” Dr. Sonett and his coauthors maintained. They include an analysis of radiologic predictors of success with thymectomy, and the role of thymectomy in seronegative MG, ocular MG and elderly patients.
“Future studies may be directed at achieving a more rapid and consistent time to a complete symptom response,” they said.
The MGTX trial does support the use of high-dose prednisone induction combined with thymectomy to achieve higher complete early remission rates, but Bio-MGTX data may help to refine induction protocols. “The debate will likely continue in regard to widespread adoption of extended transsternal maximal thymectomy,” the researchers wrote. “What was categorically measured in this trial was the effect of maximal thymectomy, as sternotomy offers no particular independent therapeutic benefit.”
The structure of the MGTX trial despite its small cohort (126) “enabled the medical and surgical community to definitively answer an important question,” they noted. Nonetheless, further investigation of the role of thymectomy in MG is “sorely needed.”
Patients may need up to 3 years to achieve an optimal response, and complete cure in a shorter time frame should be the goal for each patient. Multimodal therapy should be the basis of MG treatment. “Continued progress in the management of MG will require diligent, multidisciplinary teams designing and completing prospective studies like the MGTX,” the researchers wrote.
Dr. Sonett and his coauthors had no financial relationships to disclose. The MGTX trial was funded by the U.S. National Institute of Neurological Disorders and Stroke. There was no commercial support for the trial.