Variables
NSCLC, pneumonitis, high-grade pneumonitis, Pneumonitis
PNEUMONITIS, DISEASES, ADVERSE EVENTS, DISEASE, NSCLC, PNEUMONITIS
Patients were classified into two treatment groups. The ICI group included patients with ICI treatment (atezolizumab, nivolumab, or pembrolizumab) initiated after their advanced and/or metastatic diagnosis. Durvalumab was excluded because of its sole initial approved indication as consolidation therapy following concurrent chemoradiation in patients with locally advanced disease. Cemiplimab was excluded because of the recency of its approval for NSCLC. The chemotherapy group included patients with chemotherapy-containing regimens initiated after their advanced and/or metastatic diagnosis. Patients in the ICI group with a prior history of chemotherapy treatment were eligible for inclusion, while patients in the chemotherapy group were excluded if they had a history of ICI therapy. The intent of this exclusion is to restrict the comparison with those patients with a first exposure to ICI and those patients with no prior exposure to ICI. Patients receiving ICI or chemotherapy as consolidation therapy following definitive thoracic radiation were not indexed at the time of consolidation therapy but were indexed at treatment initiation for progressive disease (the date the therapy was received). Index treatment dates for either treatment groups were defined as the first date of an observed treatment administration of ICI or chemotherapy in the advanced and/or metastatic setting. This corresponds to when a therapy was first administered with palliative rather than definitive and/or curative intent, to align with core eligibility criteria from clinical trials. The chemotherapy group was limited to patients who received their initial chemotherapy treatment on or after January 1, 2010, as radiation practice patterns and technological changes emerging around that time period may be associated with reduced incidence of high-grade pneumonitis after definitive chemoradiation. Additional sensitivity analyses were also performed restricting the analysis to patients who received their initial chemotherapy treatment on or after January 1, 2015 to further assess comparability with the ICI treatment group.Patients with pneumonitis diagnoses were initially identified from the structured database by screening for relevant International Classification of Diseases (ICD) codes. Pneumonitis was defined using terms (including subclasses) in ICD-9 and ICD-10 that included “pneumonitis” or associated concepts in the Unified Medical Language System (TAP was defined as pneumonitis diagnosed after the index treatment start date and within 30 days of the last administration of the index treatment. Pneumonitis cases diagnosed after the 30-day window were considered treatment-associated if clinician notes explicitly attributed the pneumonitis to treatment. Because treatment-related adverse events can occur up to 2 years after treatment cessation (