BACKGROUND: Cancer treatment with immune checkpoint inhibitors (ICIs) can cause immune-related adverse events (irAEs). Incidence and onset time of irAEs vary across therapies and trials. There is lack of data regarding irAEs in veterans. The aim of this study was to evaluate irAEs in a real-world veteran population to assess the safety of ICIs.
METHODS: This is a retrospective study of United States veterans who received at least one ICI dose from 1/1/14 to 10/31/19 at VA Long Beach Healthcare System (VALBHS). The primary objectives are to describe the incidence of irAEs and time to onset after ICI therapy. The secondary objectives are to identify factors that may predict irAE occurrence and to compare the incidence and time to irAE onset at VALBHS to literature data. The irAEs evaluated were diarrhea/colitis, kidney injury, pneumonitis, thyroid disorder, and transaminitis, as defined by the National Comprehensive Cancer Network (NCCN) guidelines. Statistical analysis was performed using Fisher’s exact test, Mann-Whitney U test, and logistic regression where appropriate.
RESULTS: Of 140 evaluable patients, 31 experienced 1 or more irAEs, for a total of 37 irAEs. Baseline characteristics among patients with irAEs versus patients with no irAEs were not statistically significant except for thoracic cancer (19.4% vs. 45%, p=0.01) and number of ICI doses received (median 9 vs. 5 doses, =0.01), respectively. There were 5 incidences of diarrhea/colitis, 5 kidney injury, 2 pneumonitis, 17 thyroid disorder, and 8 transaminitis. Severity ranged from grade 1-3. The median time to irAE onset was 18 weeks (range, 1-78 weeks). The factors examined (age, gender, race, cancer type, ICI drug class, and number of ICI doses received) did not significantly predict irAE occurrence (B<0.436, >0.21). When compared to literature data, VALBHS had broadly similar irAE incidence rates, but patients generally had a longer time to irAE onset.
CONCLUSION: Incidence of irAEs in the veteran population at VALBHS is generally consistent with the literature. The longer time to irAE onset in the study underscores the importance of ongoing monitoring during ICI therapy, as irAEs can happen anytime and there were no patient factors that helped predict occurrence.