Evaluating Outcomes of Dermatomyositis Patients Treated with Immune Checkpoint Inhibitor Therapy

Summary: Background: Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment. However, there is limited data on the safety of ICIs in patients with pre-existing autoimmune diseases, including dermatomyositis (DM).1 These patients were excluded from ICI clinical trials due to concern for exacerbating underlying autoimmune disease. More studies are needed to investigate the use of ICIs in patients with autoimmune disease, particularly in DM given that patients with DM have a 6-fold increased risk of malignancy compared to the general population.2 Methods: We queried the Research Patient Data Registry of Mass General Brigham using DM-related ICD 9/10 codes to identify all patients diagnosed with DM from 2012 to 2023. All patients treated with an ICI following a diagnosis of DM were included in the study. Demographics, clinical features, and treatment data were analyzed. Results: 9 of 671 patients were treated with an ICI after DM onset (Table 1). Four patients experienced a flare of their DM following ICI therapy. Two patients had severe flares requiring cessation of therapy (Patients 7 and 8). The reason for therapy cessation was flare of interstitial lung disease and myositis, respectively. One patient (patient 7) was hospitalized. There were no cases in which a flare of cutaneous disease prompted cessation of ICI therapy. Disease activity at the time of ICI initiation was not predictive of a DM flare. Conclusions: This is the largest study to date analyzing the use of ICIs in patients with pre-existing DM. We report a similar rate of ICI discontinuation in patients with DM compared to patients without underlying autoimmune disease.3,4 Patients with skin-limited dermatomyositis are potentially less likely to discontinue ICI therapy due to a DM flare compared to those patients with classic DM or lung involvement although larger prospective studies are needed. Importantly, underlying DM should not exclude patients from treatment with an ICI, however, careful monitoring and coordination with the patient’s oncologist is critical.