Interstitial Pneumonitis Following Sequential Administration of Programmed Death-1/Programmed Death-Ligand1 Inhibitors and Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors For Non-Small Cell Lung Cancer: A Matched‐Pair Cohort Study Using a Nationwide Inpatient Database

It is unclear whether the sequential administration of programmed death (PD)-1/programmed death-ligand 1 (PD-L1) inhibitors and epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) is associated with the development of severe interstitial pneumonitis (IP). We identified 69,107 eligible patients with non-small cell lung cancer (NSCLC) from a Japanese national inpatient database, who initiated EGFR-TKI therapy. The study population was divided into the PD-1/PD-L1 inhibitor and non-prior PD-1/PD-L1 groups based on PD-1/PD-L1 administration before EGFR-TKI therapy. We conducted 1:4 matched-pair cohort analyses (n = 9,725) to compare the incidence of IP and in-hospital mortality within 90 days of administration of EGFR-TKI between the two groups after adjusting for the clinical background. Furthermore, we performed subgroup analyses categorized according to the duration of prior PD-1/PD-L1 inhibitor use. IP occurred in 4.4% of patients in the matched-pair cohort. PD-1/PD-L1 inhibitor-use before EGFR-TKI therapy was significantly associated with IP (odds ratio [OR], 1.79; 95% confidence interval [CI], 1.34-2.38) and in-hospital mortality (OR, 2.10; 95% CI, 1.72-2.55). Prior PD-1/PD-L1 inhibitor use in an interval of