Identification of risk factors for gastrointestinal irAEs associated with immune checkpoint inhibitors.

791 Background: Immune checkpoint inhibitors (ICIs) are widely used in tumor-agnostic therapy showing remarkable survival benefit in various cancer types. Gastrointestinal (GI) toxicities are common immune-related adverse events (irAEs) with limited reports for risk factors. In this study, we investigated potential risk factors for GI-irAEs in patients receiving immunotherapy. Methods: We retrospectively reviewed medical records of cancer patients treated with ICIs between January 2020 and December 2021 at Tokyo Medical and Dental University hospital, and analyzed the relationship between GI-irAEs and patients’ clinicopathological characteristics, treatment duration or the number of treatment cycles. Results: Among 474 patients, 136 were eligible for analysis. Patient characteristics were as follows: the median age, 68 years (range, 32-92); male/female, 104 (76.5%)/32 (23.5%); and cancer types were mainly GI in 36 (26.5%), head and neck in 33 (24.3%), urinary tract in 35 (25.7%), and others in 32 (23.5%). Details of ICIs were nivolumab in 47 (34.6%), pembrolizumab in 61 (44.9%), atezolizumab in 17 (12.5%), and nivolumab + ipilimumab in 11 (8.1%). GI-irAEs was observed in 29 patients (21.3%), and more frequent in female than male (OR: 3.07, 95% CI: 1.31-7.68, P=0.0146). The median number of treatment cycles to the onset of GI-irAEs from ICIs initiation was 4 (range, 1-70). Female had a shorter event-free survival than male (HR: 2.12, 95% CI: 0.914-4.9, P=0.041). There was no significant difference in gender for the number of treatment cycles to the onset of GI-irAEs from ICIs initiation. Of 17 patients (12.5%) with grade 2≤ GI-irAEs, female had trend toward higher incidence (OR: 2.63, 95% CI: 0.99-7.22, P = 0.122). The outcomes after the GI-irAEs onset were as follows: treatment continuation in 9 patients (52.9%), treatment discontinuation followed by observation in 1 (5.9%) and administration of corticosteroids in 7 patients (41.2%). Of 7 patients receiving corticosteroids, 2 resumed chemotherapy with other drugs, 2 resumed chemotherapy with same drugs, and 3 discontinued chemotherapy. Conclusions: Our results suggest that female is a potential risk factor for GI-irAEs during ICI treatment regardless of cancer types.