Racial disparities in immune-related adverse events of immune checkpoint inhibitors and association with survival based on clinical and biochemical responses

BACKGROUND: Immune checkpoint inhibitors (ICPi) cause various immune-related adverse events (irAE) with thyroid dysfunction as a commonly reported abnormality. There is increasing evidence showing positive association with development of irAE and survival. However, prior trials with ICPi had underrepresentation of minorities with < 5% African Americans. AIM: To evaluate the association between development of irAE and survival outcomes among a racially diverse patient population. METHODS: Data on patients with stage IV solid malignancies treated with programmed cell death-protein 1/programmed death ligand 1 blockers between January 2013 and December 2018 across MedStar Georgetown Cancer Institute facilities were retrospectively reviewed. Patients treated with cytotoxic T-lymphocyte-associated protein 4 inhibitors were excluded. Progression free survival (PFS) and overall survival (OS) were primary endpoints and were calculated using Kaplan-Meier methods and Wilcoxon rank sum test for comparison. RESULTS: Out of 293 patients who met eligibility criteria, 91 pts (31%) had any grade irAE; most common AE were endocrine (40.7%) specifically TSH elevation, dermatological (23.1%) and rheumatologic (18.7%). Proportion of irAE was significantly higher in Caucasians vs African Americans (60.4% vs 30.8%), in patients with low programmed death ligand 1, lower LDH, older age, and those who had more treatment cycles with ICPi. Rate of progression was lower in patients with irAE (30.8% vs 46.0%, P = 0.0140). Median PFS (5.8 vs 3.0 mo, P = 0.0204) and OS (17.1 vs 7.2 mo, P < 0.0001) were higher with irAE. Statistically significant difference in OS (17.1 vs 8.6 mo, P = 0.0002) but not in PFS (5.8 vs 3.3 mo, P = 0.0545) was noted with endocrine irAE. No differences in survival were observed among other commonly reported irAE. Differences in survival among subgroups of patients with irAE are described. CONCLUSION: Development of irAE positively correlated with improved PFS and OS as reported in previous studies. To our knowledge, this is the first study observing differences in OS favoring endocrine AE and Caucasian race. These factors may be potential surrogate markers of prognosis pending replication of these results in large-scale studies.