Early Success After Thymectomy Predicts Long-term Benefits for MG Patients, Study Finds

Achieving minimal disease symptoms six months after thymectomy predicts favorable long-term outcomes in people with myasthenia gravis (MG), a study suggests. The research also found that shortness of breath prior to surgery is associated with worse treatment outcomes.

The study, “Prognostic Analysis of Thymoma-Associated Myasthenia Gravis (MG) in Chinese Patients and Its Implication of MG Management: Experiences from a Tertiary Hospital,” was published in the journal Neuropsychiatric Disease and Treatment.

Up to 20% of people with MG have a thymoma, a type of benign tumor in the thymus gland. Thymoma in someone with MG is referred to as thymomatous myasthenia gravis (TMG).

The standard-of-care for TMG is thymectomy, which is surgical removal of the thymus. Understanding which factors are associated with better or worse long-term treatment outcomes following thymectomy in people with TMG is an ongoing area of investigation.

To address this knowledge gap, researchers at Central South University, in China, analyzed clinical and demographic data of 70 people with TMG who underwent thymectomy. Mean age at MG onset was 45.3 years, and mean age at thymectomy was 45.9. The median time from MG onset to thymectomy was four months, and the median disease duration was 48 months (four years).

All patients had at least a year of follow-up since diagnosis. Also, all those who were tested had anti-acetylcholine receptor antibodies.

Among patients with available data, 21 received  no anti-myasthenic treatment before thymectomy. The most common regimen was glucocorticoids or other immunosuppressants.

After thymectomy MG symptoms changed only slightly, with the exception being fewer patients presenting with ocular (vision) symptoms. Most patients started anti-myasthenic treatment within six months, with the most frequent option (in 68.6% of patients) being glucocorticoids.

Two groups were defined based on clinical status at the most recent clinical exam; 57 achieved a Myasthenia Gravis Foundation of America post-intervention status of minimal manifestation (MM) or better, while the remaining 13 did not. MM status generally means that an individual is not experiencing functional impairment due to MG, thereby suggesting remission, but they may have some muscle weakness upon clinical examination.

When the team looked for factors significantly associated with whether or not individuals achieved MM status in the long-term, statistical models revealed that outcomes at six months after thymectomy were significantly predictive of long-term status. Specifically, people who had MM status six months after thymectomy were about 23.5 times more likely to have MM status at their most recent clinical exam compared to patients with worse short-term outcome.

Also, people who experienced shortness of breath (dyspnea) before surgery were about 80% less likely to achieve long-term MM status than patients without that complication.

“Early achievement of MM-or-better status may indicate a good treatment outcome in the long run. Dyspnea symptoms before thymectomy may be associated with a poor prognosis,” the researchers wrote. “Thus, we recommend aggressive anti-myasthenic treatment for TMG patients, especially those with dyspnea symptoms, to reach MM-or-better status as soon as possible.”

Other assessed factors — including disease duration, MG treatment after surgery, and thymoma type — were not significantly associated with long-term outcomes.

Notably, people who achieved long-term MM status tended to wait less time for thymectomy since MG manifestation. However, this difference was not statistically significant, which the researchers said could be due to the small number of participants. As such, early removal of thymoma may be beneficial in the long-term, they added.