Rheumatic Immune-Related Adverse Events: Immune Checkpoint Inhibitor Therapy and Ramifications for Health Disparities

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy; however, they have been associated with clinically significant immune-related adverse events (irAEs), including rheumatic irAEs. Rheumatic irAEs due to ICIs are not well characterized among ethnic minorities.

Accordingly, we investigated rheumatic irAEs and referrals to rheumatologists at a public medical center (MC) serving a predominantly Hispanic population and a neighboring private MC serving a predominantly a population that identified as White, Black, Asian, or Indigenous population, with each MC being staffed by faculty from the same medical school.

The medical records of patients 18+ years seen at either MC from May 2015 through May 2021 were screened for treatment with ICIs by ICD codes. We compared characteristics of ICI-treated patients who developed irAEs vs. those who did not develop irAEs. Overall, 28 (20.9%) and 74 (15.5%) patients developed documented irAEs at the public and private MCs, respectively. Of these, 21 patients (six at the public MC; 15 at the private MC) developed rheumatic irAEs. We compared referral rates to rheumatologists and management of rheumatic irAEs between these two groups.

Across both MCs, the most common rheumatic irAEs were arthritis (66.7%) and myositis (14.3%). Compared to private patients, public patients were more likely to be Hispanic (66.7% vs. 13.3%, p=0.012) and less likely to be referred to a rheumatologist (16.7% vs. 66.7%, p=0.036). There were no significant differences between institutions in cancer outcomes in patients with rheumatic iRAEs.

The significantly lower rate of referrals to rheumatologists among patients with rheumatic irAEs at a public MC compared to patients at a neighboring private MC raises concern for healthcare disparities. Larger studies with racially diverse patients are necessary to help ensure equitable care for all patients.