Purposive sampling was employed to select participants who met the specific inclusion criteria, focusing on patients diagnosed with non-small cell lung cancer (NSCLC) and treated with immune checkpoint inhibitors (ICI) (nivolumab, pembrolizumab, atezolizumab, or durvalumab) during routine clinical practice. The study specifically targets patients who received their first ICI therapy between December 31, 2014, and December 31, 2021. Participants are restricted to those diagnosed with NSCLC within 2 years prior to the date of first ICI administration. Patients with documented pregnancy within 180 days prior to the enrollment date were excluded, as were those under 18 years of age or over 100 years of age at the time of enrollment. Individuals with a history of any primary malignancy other than lung cancer within 2 years prior to the enrollment date and those who received concomitant anticancer therapies such as taxane, platinum, pemetrexed, etoposide, doxorubicin, gemcitabine, irinotecan, vinorelbine, vinblastine, or bevacizumab at the index date were also excluded. All participants were identified retrospectively from clinical data models (CDM) or electronic medical records (EMRs) across five institutions: Seoul National University Hospital, Bundang Seoul National University Hospital, Pusan National University Hospital, and the Catholic Medical Center of Korea. To minimize selection bias inherent to observational studies, time-dependent propensity score matching was performed, simulating pseudo-randomization to balance baseline characteristics between groups.
