12130 Background: Immune checkpoint inhibitors (ICIs) have emerged as a core pillar of lung cancer (LC) therapy, but ICIs are commonly associated with a spectrum of immune-related adverse effects (irAEs). The real-world patterns and risk factors of irAEs in LC remain uncertain. Methods: Patients with LC newly started on ICIs between 10/01/2018 and 09/30/2021 were retrospectively collected from the Tufts Medical Center cancer registry and pharmacy records. irAEs occurring within 12 months after initiation of ICIs were identified. Univariable logistic regression was used to assess the risk factors of irAEs. Those with p-value<0.20 were included in multivariable logistic regression analysis (MVA), along with clinically relevant factors. Results: Of 125 LC adult patients (median age: 70 years, 68 males), 104 had non-small cell lung cancer (NSCLC), 123 had advanced stages, and 16 had preexisting autoimmune diseases (ADs). Six patients were treated with dual-agent ICIs. Pembrolizumab was the most often used single agent (67.2%). In total 50 irAEs occurred in 39 patients. The most common irAEs were endocrinopathies (34%), pneumonitis (20%), dermatitis (14%), and gastrointestinal toxicity (14%) with the median onset time of 148, 136, 19, and 68 days, respectively. 70% of irAEs were grade 1 or 2. 44% of irAEs were treated with immunosuppression, 38% were referred to specialist care, and 30% required hospitalizations. 56% of irAEs resolved within 12 months and 67.9 % of those were rechallenged with ICIs. In exploratory univariable analyses among all the patients, age, small cell lung cancer (SCLC), PDL1 positivity (TPS≥1%), concurrent NSAIDs use, and radiation therapy had p< 0.2. In MVA, SCLC remained significantly associated with irAEs (OR=4.14, 95% CI [1.50, 12.09], p=0.007). Among NSCLC subset (N=104), age, PDL1 positivity, concurrent NSAIDs, and acetaminophen use had p<0.2. Age (OR=0.94, 95% CI [0.883, 0.990], p=0.026) and PDL1 positivity (OR=3.17, 95% CI [1.12, 9.87], p=0.036) remained significant in MVA (Table). Conclusions: Our study described the real-world patterns of irAEs in LC patients. SCLC was found to be an independent risk factor of irAEs in our cohort. In NSCLC, younger age and PDL1 positivity were associated with irAEs occurrence. Future studies are required to validate these findings in larger samples. [Table: see text]