International Myositis Assessment and Clinical Studies Guidelines for Risk-Based Cancer Screening: An External...

Dermatomyositis (DM) is an idiopathic inflammatory myopathy (IIM) characterized by muscle weakness, skin findings, and increased malignancy risk. Cancer risk is greatest in the three years before or after DM onset, termed paraneoplastic DM. The International Myositis Assessment and Clinical Studies Group (IMACS) set forth evidence-based guidelines for risk stratification and cancer screenings for newly diagnosed patients with IIM.

We retrospectively reviewed the records of 413 patients with a known diagnosis of DM or clinically amyopathic DM at the Mount Sinai Health System (2019-2024). Demographics, clinical findings, laboratory results, myositis autoantibody panels, and cancer screening or diagnosis data were collected.

Among the 413 patients with DM, 6.5% (n = 27) had paraneoplastic DM. The proportion of paraneoplastic disease was highest in the high-risk group (8.8%), compared to intermediate- (5.1%) and low-risk (2.5%) groups. 70.4% of patients with paraneoplastic DM were categorized as high risk, compared to 51% of nonparaneoplastic patients. Among the intermediate-risk patients, most patients were diagnosed with cancer more than one year after DM diagnosis. Age ≥40 at DM diagnosis was statistically significant for an increased risk of paraneoplastic DM (P = 0.001). The most common paraneoplastic malignancies were breast cancer and lung cancer. One-third of patients with paraneoplastic DM were diagnosed with cancer within three years preceding DM diagnosis.

The IMACS screening guidelines and risk stratification showed moderate sensitivity for identifying paraneoplastic DM, helping to identify a majority of patients at the highest risk for malignancy leading to more targeted and risk-based screening.