A study recently published in Frontiers in Immunology found that immune checkpoint inhibitors (ICIs), a type of drug that helps the immune system fight cancer, may trigger life-threatening complications when used to treat thymomas in people with myasthenia gravis (MG).
Between 10% and 15% of patients with anti-acetylcholine receptor (AChR) antibody-positive MG have thymomas, or cancer of the thymus. To better understand if ICIs caused side effects when used to treat these patients, the study’s authors examined how ICI affected six patients with thymomas and MG and compared them to ICI in 10 patients with thymomas but without MG.
All patients with MG developed severe side effects, notably inflammation of the heart muscle (called myocarditis). Half of the patients with MG died, all due to myocarditis. In comparison, only 40% of those without MG developed severe side effects.
All patients with MG also experienced worsening symptoms, with many progressing to myasthenic crisis, a severe complication in which muscle weakness worsens and can interfere with breathing. Most complications occurred early, often after the first treatment cycle.
Immunotherapy with ICIs is often used when other treatments are no longer effective, making it an important option for some patients with advanced disease. They work by activating the immune system to attack cancer cells, but this same effect can also cause it to mistakenly target healthy tissues in people with autoimmune conditions such as MG, leading to worsening symptoms and serious complications.
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The findings also suggest that strategies to manage immune-related complications may improve outcomes. Patients who were already receiving immunosuppressive medications before starting immunotherapy tended to experience better results. In addition, early treatment with a combination of steroids and intravenous immunoglobulin (IVIG) during complications was associated with improved outcomes, compared with using either treatment alone. These therapies are commonly used to reduce immune activity and control inflammation during severe reactions.
The results highlight the importance of careful observation and treatment planning if ICI therapy is used in people with MG and thymoma. “For MG patients with thymoma who receive one session of ICI therapy, close monitoring is recommended because of the high incidence of severe myocarditis and [myasthenic crisis],” said the study’s authors. Careful patient selection may also help reduce the risk of serious complications.
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