Project Summary One of the most significant advancements in lung cancer treatment has been the introduction of immune checkpoint inhibitors (ICIs), which either as single agents or in combination with platinum-based chemotherapy, are now front-line therapy for most patients with metastatic non-small cell lung cancer (NSCLC). While treatment response rates can be remarkable, side effects, especially immune-related adverse events (irAEs), are of major concern. When uncontrolled, side effects can result in unscheduled care, increased out-of-pocket costs for patients, and treatment delays or discontinuation. African Americans continue to have worse outcomes after a lung cancer diagnosis than whites, and there are known differences between African Americans and whites with respect to many aspects of cancer treatment, including time to initiation and dose of chemotherapy, symptom burden, and even treatment of side effects. However, little is known about potential differences by race with respect to response to ICI treatment largely due to a lack of inclusion of African American patients in the clinical trials leading to FDA approvals. Thus, there is a critical need to explore whether African American and white patients are differentially impacted by side effects related to ICI treatment. The specific aims are to: 1) Characterize patient-reported side effects and quality of life and clinician-assessed irAEs associated with ICI treatment in a group of African American and white lung cancer patients being treated in a standard care setting; and 2) Identify the sociodemographic, individual, and disease-specific determinants of patient-reported side effects and quality of life and irAEs associated with ICI treatment and characterize differences by race. While ICIs holds promise for improved outcomes, little is known about whether potential predictors of patient-reported side effects and quality of life and irAEs vary by race. This study will directly evaluate multi-level predictors in response to ICI treatment in African American and white patients. Understanding the sociodemographic, individual, and disease-specific determinants of these outcomes in lung cancer patients provides the basis for moving towards a more equity-focused approach to the use of ICIs. By identifying drivers of potential disparities, we can better identify patients at high risk for side effects and irAEs, develop interventions to reduce risk factors, thereby improving patient quality of life and reducing racial disparities in outcomes.