Correlation between lymphocyte counts and PD-L1 immune-related adverse events

IntroductionImmune checkpoint inhibitors have improved outcomes for solid tumors but are associated with immune-related adverse events (irAEs). Literature suggests that patients with an absolute lymphocyte count (ALC) ≥ 2000 cells/mm3 prior to treatment with PD-1 inhibitors have an increased risk for irAEs, but the relationship between ALC and irAEs has not been examined with PD-L1 inhibitors. This study evaluates the correlation between ALC and PD-L1 inhibitor related irAEs.MethodsThis retrospective cohort study at an academic health system used electronic health record data from adult patients with solid tumors receiving their first dose of a PD-L1 inhibitor between January 1, 2022, to December 31, 2023. Patients were excluded if they did not have a baseline ALC within 30 days of initial treatment, had a prior irAE(s), had a hematologic malignancy, received any other immunotherapy prior to or during the study period, or were treated with corticosteroids within 1 month prior to treatment.ResultsAmong 210 patients, 186 had a baseline ALC < 2000 cells/mm3 and 24 had a baseline ALC ≥ 2000 cells/mm3. 20 grade 2 + irAE events occurred, 19 in patients with an ALC < 2000 cells/mm3 and only 1 in patients with a baseline ALC ≥ 2000 cells/mm3. There was no correlation between a baseline ALC ≥ 2000 cells/mm3 and incidence of grade 2 + irAE (OR 0.503; 95% CI: 0.064, 3.98; P = 0.515).ConclusionIn this cohort study of patients treated with PD-L1 immune checkpoint inhibitors, baseline ALC ≥ 2000 cells/mm3 did not predict PD-L1 inhibitor related irAEs.