Abstract C170: Unveiling sex differences in hospitalization rates for immune-related adverse events in older lung cancer patients treated with ICIs: A SEER-Medicare analysis
Authors: Nikita Fnu , Sharma Swapnil , Shaver Amy , Gandhi Krupa , Keith Scott W. , Malfer Christina Steinbock- , Johnson Jennifer M. , Gordon Sarah , Lu-Yao Grace 
Published: September 2024

Abstract
Introduction Immune checkpoint inhibitors (ICIs) offer substantial benefits for older adults with lung cancer (LCa) but they also pose risks of immune-related adverse events (irAEs), necessitating investigation into the demographic influences on hospitalization rates. Sex differences among older adults within this cohort are understudied. Our study aims to explore the gender differences in irAE-related hospitalizations among older adults. Methods We utilized Surveillance, Epidemiology, and End Results (SEER)-linked Medicare data to identify older adults diagnosed with primary LCa from 1999 to 2017 and treated with ICIs between 2011 and 2019. Patients were steroid-naïve and chemo-naïve for 3 and 12 months, respectively, prior to ICI initiation. ICD-9/10 diagnosis codes were used to identify irAEs post-ICI initiation and these diagnosis were flagged during the pre-ICI period for comparison. An adjusted negative binomial model compared irAE-hospitalization rates in the post-ICI period (0-6, 7-12, and 13-24 months) to those in the pre-ICI period (6 months prior), accounting for confounders. An interaction term between gender and treatment period was included to compare differences in rates between males and females. Results Of the 1,089 patients, 54% were female, 79.6% had Charlson Comorbidity Index (CCI) ≥1. Females had 59% higher rates of irAE-hospitalizations at baseline (95% CI: 1.18 – 2.14, p&lt;0.001). Patients with CCI≥3 had a 141% higher rate for irAE- hospitalization compared to those with CCI=0. Specifically for males, compared to 6-months pre-ICI, the irAE-hospitalization rates were 187% higher 0-6 months post-ICI (IRR = 2.87, 95% CI: 1.20-3.74), 134% higher 7-12 months post-ICI (IRR = 2.34, 95% CI: 1.66-3.31), and 122% higher 13-24 months post-ICI (IRR = 2.22, 95% CI: 1.53-3.28). Similarly for females, compared to 6-months pre-ICI, the irAE-hospitalization rates were 123% higher 0-6 months post-ICI (IRR = 2.23, 95% CI: 1.27-3.75), 69% higher 7-12 months post-ICI (IRR = 1.69, 95% CI: 1.27-3.37), and 11% higher 13-24 months post-ICI (IRR = 1.11, 95% CI: 1.03-2.37). Age and race did not impact irAE-hospitalization rates among LCa patients. Conclusions The incidence of irAEs following ICI treatment is notably higher in the first six months post-ICI for both males and females, with males experiencing a higher rate of events across all post-treatment periods. Key factors influencing the rate of irAE-hospitalizations include the CCI and pre-treatment gender differences. These findings underscore the need for tailored post-ICI monitoring strategies to mitigate adverse events in vulnerable populations.
Citation Format: Fnu Nikita, Swapnil Sharma, Amy Shaver, Krupa Gandhi, Scott W. Keith, Christina Steinbock- Malfer, Jennifer M. Johnson, Sarah Gordon, Grace Lu-Yao. Unveiling sex differences in hospitalization rates for immune-related adverse events in older lung cancer patients treated with ICIs: A SEER-Medicare analysis [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C170.