Patients with myasthenia gravis (MG) may face a higher risk of developing certain cancers, particularly around the time of diagnosis, according to research published recently in Muscle and Nerve.
In a large case-control study using the Clalit Health Services database, investigators analyzed 1,558 adults with a high probability of MG and compared them with 4,674 age- and sex-matched controls. A machine learning model helped confirm diagnoses with strong performance, including 91% accuracy and an area under the curve of 0.97, reducing the chance of misclassification.
“Our study established a significant association between MG and malignancy, both in the years before and after MG diagnosis,” stated the study’s investigators.
The findings showed that patients with MG were nearly twice as likely to have had cancer before their diagnosis. The risk was especially elevated in the year leading up to diagnosis, when 13.6% of patients had cancer compared with 4.8% of controls.
After diagnosis, cancer risk remained higher. About 25.2% of patients with MG developed malignancies compared with 16.7% of controls. The risk was greatest in the first three years following diagnosis. The most common cancers included those affecting the respiratory and intrathoracic regions, nonmelanoma skin cancer, urinary tract tumors, soft tissue cancers and myelodysplastic syndrome (a form of blood cancer).
Read more about the prognosis of MG
Certain factors increased the likelihood of cancer within the MG population. Older age, male sex and the presence of thymoma were all linked to higher risk. In contrast, acetylcholine receptor antibody status was not associated with malignancy. Importantly, treatments such as prednisone, azathioprine, rituximab and mycophenolate did not independently raise cancer risk.
For patients, these findings suggest that the disease itself, rather than its treatment, may underlie the increased cancer risk. Experts say this could be due to immune system dysregulation. The results support considering cancer screening at diagnosis and during the first three years after, especially for higher-risk individuals. Suggested approaches include chest imaging, skin exams and routine blood tests, though further studies are needed to confirm the benefits of screening.
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