Among people with myasthenia gravis (MG) and thymoma — a tumor of the thymus — being male and having more severe disease, advanced thymoma, or post-surgery complications predict poorer outcomes, a study from China suggests.
In turn, anticholinesterase therapies taken early and before surgery to remove the thymus were associated with better long-term outcomes in this group of MG patients.
Data also supported closer monitoring of potential thymomas in middle-aged and elderly MG patients who have antibodies against acetylcholine receptors (AChR), one of the main causes of MG.
The study, “Thymomatous myasthenia gravis: 10‐year experience of a single center,” was published in the journal Acta Neurologica Scandinavica.
Current estimates indicate that 10%–15% of people with thymoma develop MG, while about 30% of MG patients simultaneously have a thymoma (called T-MG). The surgical removal of the thymus — called a thymectomy — is indicated for all MG patients, regardless of their MG type.
While research suggests that T-MG patients usually have a worse prognosis than other subgroups of people with MG, data on the clinical features, long-term prognosis, and outcome predictors of T-MG patients are limited.
Researchers at The First Affiliated Hospital of Sun Yat-sen University analyzed clinical and demographic data of 196 MG patients (100 with T-MG, and 96 without thymoma or NT-MG) treated at their hospital over 10 years.
Results showed significant differences between T-MG and NT-MG patients. Disease onset occurred significantly later among people with T-MG (45.66 years vs. 39.06 years in NT-MG patients), as reflected in a higher proportion of disease onset after age 40 (72% vs. 40.6%).
Compared with patients without thymoma, a significantly higher proportion of those with thymoma had antibodies against AChR (100% vs. 83.3%), more severe disease — 61% vs. 33% — and poorer outcomes, 26% vs. 6.3%.
These findings suggest that “clinicians should be alert to middle-aged and elderly patients presenting with MG with AChR-[antibody] positivity,” the researchers wrote, adding that CT examination of the thymus “is highly recommended in such patients to verify the presence of a thymoma.”
A closer outcomes analysis showed disease reduction — not including complete remission — being achieved in most NT-MG patients (83.3%), and 50% of those with thymoma.
Notably, while the presence of thymoma was associated with poorer outcomes (unchanged or worsening disease), a significantly higher proportion T-MG patients achieved disease remission, compared with those without thymoma (24% vs. 10.4%).
“The coexistence of extremely high rates of [disease remission] and deterioration and mortality of T-MG patients may be key to the inconsistent conclusions of previous studies,” the researchers wrote.
They next evaluated potential factors associated with poorer or better outcomes in all participants.
Data showed that the presence of thymoma was significantly associated with a poor prognosis, influencing long-term outcomes even in patients who underwent thymectomy.
In T-MG patients, being male, having more severe disease, more advanced thymoma (more likely spread outside the thymus), and post-thymectomy complications were significant predictors of poorer long-term outcomes.
This highlighted that “understandably, T-MG is not only affected by the clinical factors of MG but also by the [disease-associated] factors of the thymoma,” the researchers wrote.
In turn, T-MG patients given anticholinesterase treatments — such as Mestinon (pyridostigmine, by Bausch Health) — early and before thymectomy were significantly more likely to show better outcomes than those not using such therapies.
Based on these findings, the team hypothesized that an early diagnosis and timely treatment may help to prevent thymoma progression in MG patients, ultimately leading to better prognosis.
“A comprehensive understanding of the characteristics of T-MG will likely help improve its prognosis,” the scientists wrote, adding that “it is essential to validate our findings with a larger patient sample, improve the follow-up data, and form a systematic clinical database.”
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