Background: The risk and survival of patients with non-small cell lung cancer (NSCLC) with pre-existing autoimmune disorders (AIDs) receiving immune checkpoint blockade (ICB) therapy have not been clearly established., Patients and Methods: This multi-institutional, retrospective cohort study was conducted in collaboration with 20 centers in Japan., Results: In total, 229 patients with advanced or recurrent NSCLC and pre-existing AID, with or without ICB treatment from January 2010-February 2020, were included and analyzed. Among 69 patients who received ICB, 2 received two lines of ICBs with a total of 71 ICB treatments; 57 (80.3 %) and 14 (19.7 %) patients received ICB monotherapy and combination therapy, respectively. AID flares were observed in 18 patients (25.4 %, 95 % confidence interval [CI], 15.8-37.1 %) receiving ICB. AID exacerbations were more likely when NSCLC was diagnosed less than 1 year after the AID diagnosis (odds ratio 5.26 [95 % CI, 1.40-21.61]; P = 0.016). Immune-related adverse events were observed in 32 patients (45.1 %, 95 % CI, 33.2-57.3 %); 17 had grade 3 or higher. The safety profile of combination immunotherapy was not significantly different from that of the monotherapy. After inverse probability weighting, the use of ICB prolonged survival (hazard ratio 0.43 [95 % CI, 0.26-0.70]; P = 0.0006)., Conclusions: These findings revealed a novel risk factor for AID flares following ICB treatment, that is the diagnosis of NSCLC within 1 year of AID diagnosis, and showed that ICBs may improve survival in this population. These results support the utilization of ICB in patients with NSCLC and pre-existing AID., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Dr. Asao reported receiving personal fees from AstraZeneca, Boehringer Ingelheim, Bristol Myers Squibb, Chugai Pharmaceutical, Daiichi Sankyo, Eli Lilly Japan, Merck Biopharma, MSD, Nippon Kayaku, Ono Pharmaceutical, Pfizer, Taiho Pharmaceutical, and Takeda Pharmaceutical outside the submitted work. Dr. Shukuya reported receiving grants from AstraZeneca, Boehringer Ingelheim, Chugai Pharmaceutical, MSD, and Novartis, outside the submitted work; and personal fees from AstraZeneca, Boehringer Ingelheim, Bristol-Myers Squibb, Chugai Pharmaceutical, Daiichi Sankyo, Eli Lilly, MSD, Nippon Kayaku, Novartis, Ono Pharmaceutical, Pfizer, Taiho Pharmaceutical, Takeda Pharmaceutical, outside the submitted work. Dr. Mouri reported receiving personal fees from Chugai Pharmaceutical and Eli Lilly, outside the submitted work. Dr. Tsukita reported receiving personal fees from AstraZeneca, Boehringer Ingelheim, Bristol-Meyers Squibb, Chugai Pharmaceutical, Daiichi-Sankyo, Eisai, Eli Lilly, MSD, and Taiho Pharmaceutical, outside the submitted work. Dr. Watanabe reported receiving grants from Nippon Kayaku outside the submitted work, personal fees from AstraZeneca, Bristol-Meyers Squibb, Celltrion, Chugai Pharmaceutical, Daiichi-Sankyo, Eli Lilly, Kyowa Kirin, MSD, Nippon Kayaku, Novartis, Ono Pharmaceutical, Taiho Pharmaceutical, Takeda Pharmaceutical, outside the submitted work. Dr. Morita reported receiving personal fees from Amgen, AstraZeneca, Bristol-Meyers Squibb, Chugai Pharmaceutical, Daiichi-Sankyo, Eli Lilly, MSD, Nippon Kayaku, Novartis, Pfizer, Taiho Pharmaceutical, Takeda Pharmaceutical, and ThermoFisher Scientific, outside the submitted work. Dr. Yoshioka reported receiving grants from AstraZeneca, Boehringer Ingelheim, Daiichi Sankyo, Delta Fly Pharma, Janssen Pharmaceutical, MSD, and Novartis, outside the submitted work; and personal fees from AstraZeneca, Amgen, Boehringer Ingelheim, Bristol-Myers Squibb, Chugai Pharmaceutical, Daiichi Sankyo, Eli Lilly, Kyowa Kirin, MSD, Nippon Kayaku, Nipro Pharma, Novartis, Ono Pharmaceutical, Otsuka Pharmaceutical, Pfizer, Taiho Pharmaceutical, outside the submitted work. Dr. Namba reported receiving personal fees from Chugai Pharmaceutical, Kyowa Kirin, MSD, and Taiho Pharmaceutical, outside the submitted work. Dr. Nakagawa reported receiving personal fees from AstraZeneca, Chugai Pharmaceutical, Eli Lilly Japan, Japan Blood Products Organization, MSD, Nippon Kayaku, Novartis Pharma, Ono Pharmaceutical, Pfizer Japan, and Taiho Pharmaceutical, outside the submitted work. Dr. Watanabe reported receiving grants from MSD, outside the submitted work. Dr. Kobayashi reported receiving personal fees from AstraZeneca and Takeda Pharmaceutical, outside the submitted work. Dr. Takahashi reports grant support from Asahi Kasei Pharma, Bayer, Boehringer Ingelheim, Chugai Pharmaceutical, Daiichi Sankyo, Eli-Lilly, Kyorin Pharmaceutical, Kyowa Kirin, Nippon Kayaku, Nippon Shinyaku, Nipro Pharma, Novartis, Ono Pharmaceutical, Pfizer, Sanofi, Shionogi, Takeda Pharmaceutical, Taiho Pharmaceutical, Teijin Pharma, and Tsumura, outside the submitted work; personal fees from Abbott Japan, AstraZeneca, Boehringer Ingelheim, Bristol-Myers Squibb, Chugai Pharmaceutical, Eli Lilly, Janssen Pharmaceutical, Meiji Seika Pharma, Merck Biopharma, MSD, Kyorin Pharmaceutical, Nippon Kayaku, Novartis, Ono Pharmaceutical, Pfizer, Sumitomo Dainippon Pharma, Taiho Pharmaceutical, Takeda Pharmaceutical, ThermoFisher Scientific and Viatris, outside the submitted work.; and serving as a board member of director of the Japan Lung Cancer Society and The Japanese Respiratory Society. No other disclosures were reported., (Copyright © 2024. Published by Elsevier B.V.)