Background/Purpose: Patients with cancer treated with CPI can develop irAEs. Since immune changes may impact blood counts and ratios, we hypothesized that those would be associated with irAEs. We also investigated the association between irAEs and personal or family history of autoimmune disease (AD), combination of CPI and/or history of chronic infection.

Methods: We performed a retrospective cohort study and identified patients with solid and hematologic malignancies who started CPI (anti-PD1/PDL1 and anti-CTLA-4) in 2018. We defined irAEs as both rheumatologic and non-rheumatologic. The association between irAEs, baseline absolute neutrophil (ANC), lymphocyte (ALC), monocyte count (AMC), neutrophil to lymphocyte (NLR), monocyte to lymphocyte (MLR), platelet to lymphocyte ratio (PLR), was assessed by logistic regression (LR) with robust standard errors adjusting for age, sex, smoking history, cancer type, ECOG performance status (PS), concomitant systemic therapy, personal or family history of AD and chronic infection. LR with robust standard errors was also used to examine the relationship between irAEs and personal or family history of AD, combination of CPI and chronic infection adjusting for age, sex, smoking history, cancer type, ECOG PS, and concomitant systemic therapy. After Bonferroni correction, alpha level was set to 0.005 for all statistical testing.

Results: A total of 193 patients were identified with median age 64 (range 23-92), 47% women; 49% with smoking history; 23% had lung cancer, 21% skin cancer, 56% other cancers; 19% received concomitant CPI and 32% other systemic therapy plus CPI. Rheumatologic irAEs were reported in 10%, and non-rheumatologic irAEs in 23% of patients. Association between irAEs, blood biomarkers and clinical features are described in Table. Development of irAEs was significantly associated with higher baseline ALC (OR: 2.43, 95%CI: 1.39-4.22, p=0.002) and lower baseline MLR (OR: 0.09, 95%CI: 0.02-0.42, p=0.002). Patients with pre-existing AD (OR: 5.14, 95%CI: 2.18-12.15, p< 0.001) were also more likely to experience irAEs during treatment with CPI.

Conclusion: In patients with cancer treated with CPI, irAE development was associated with higher baseline ALC, lower MLR and pre-existing history of AD. Further validation is required to test our generated hypothesis that blood count subsets could be used as inexpensive and easily obtained biomarkers to predict the development of irAEs in clinical practice.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/association-of-blood-count-biomarkers-and-clinical-features-with-immune-related-adverse-events-iraes-in-patients-with-cancer-treated-with-checkpoint-inhibitors-cpi/