Background: There is increasing clinical and research interest in patient-reported outcomes (PROs) which provide unique and complementary information to provider-rated adverse events. While several studies have been published of PROs in lung cancer patients receiving immune checkpoint blockade, to our knowledge all have focused on PROs collected as part of a clinical trial. This interim analysis describes PROs outside the context of a clinical trial. Methods: The Addario Lung Cancer Foundation (ALCF) international patient registry was used to collect patient-reported clinical and PRO information. Patients who reported current or past treatment with an FDA-approved immune checkpoint inhibitor were asked to complete a second survey of symptomatic toxicities of these therapies. Patients rated 40 symptoms on a five-point scale. The Charlson Comorbidity Index and Functional Assessment of Cancer Therapy General (FACT-G) were administered to assess comorbidities and quality of life, respectively. Results: A total of 116 patients (mean age 61, 75% female) who reported treatment with nivolumab (52%) or pembrolizumab (47%) were included in analyses. The majority of patients (70%) had been treated for 6 months or less. The most commonly reported symptoms were fatigue (72%), aching joints (52%), aching muscles (35%), insomnia (34%), back pain (30%), itching (27%), bone pain (26%), and skin dryness (25%). A total of 26% of patients had experienced a treatment delay, 10% had been to the emergency room, and 6% had been hospitalized due to toxicity. Participants reported a mean score of 75.88 (SD=17.59) on the FACT-G, significantly lower than previously-published normative data for cancer patients. Conclusions: This study is among the first to evaluate patient-reported toxicities of immune checkpoint inhibitor outside the context of a clinical trial. Results from this interim analysis indicate patient reported toxicities of immune checkpoint inhibitors are common in lung cancer patients. Additional research is needed to better understand the longitudinal course of symptomatic toxicities. Acknowledgements: ALCF, IASLC, American Lung Association.