Chaeuk Chung

Cancer‐associated dermatomyositis (CAD), a paraneoplastic syndrome characterized by dermatomyositis (DM), frequently presents in association with small cell lung cancer (SCLC). Although the advent of immune checkpoint inhibitors (ICIs) has revolutionized cancer treatment, their efficacy and safety in patients with concurrent autoimmune diseases (AD) and malignancies remains uncertain. Several studies have suggested the safe administration of ICIs in patients with AD, indicating that successful cancer therapy can alleviate CAD symptoms. Conversely, other studies have raised concerns about the potential for ICIs to exacerbate AD flares or immune‐related adverse events (irAEs). A comparative analysis of two cases from our institution emphasizes the variability in ICI responses among SCLC patients with CAD. One patient, previously reported as a case study, exhibited significant clinical improvement in DM symptoms after ICI administration, whereas the other developed severe exfoliative skin changes and experienced an unfavorable prognosis. This variability emphasizes the need for careful patient selection and close monitoring during ICI treatment. We hypothesized that overweight or obese individuals and those with severe initial skin lesions and elevated lactate dehydrogenase levels are more susceptible to developing irAEs following ICI therapy. Therefore, caution is advised when considering immunotherapy in these patients.