Risk of pneumonitis in non-small cell lung cancer patients with preexisting interstitial lung diseases treated with immune checkpoint inhibitors: a nationwide retrospective cohort study.

BACKGROUND: Chemotherapy for non-small cell lung cancer (NSCLC) patients with preexisting interstitial lung diseases (ILDs) increases the risk of developing pneumonitis. However, the association between pneumonitis and immune checkpoint inhibitors (ICIs) and related factors remains unclear. METHODS: We conducted a retrospective cohort study using a nationwide inpatient database. We included patients (aged ≥ 20 years) newly diagnosed with ILD and NSCLC and who started chemotherapy (ICIs or conventional chemotherapy) between January 2016 and December 2019. The primary endpoint was the onset of pneumonitis. We estimated the cumulative incidence function of pneumonitis and compared it with patients taking ICIs and patients receiving conventional chemotherapy using Gray's test. We calculated the subdistribution hazard ratios (HRs) and 95% confidence intervals (CIs) for the incidence of pneumonitis using Fine and Gray's model to adjust for sex, age, smoking status, histology of NSCLC, surgical history, and medical histories, considering death as the competing risk. RESULTS: We identified 1177 patients (mean age 72 years, 13.8% female), of which 328 and 849 were in the ICI and conventional chemotherapy groups, respectively. There was no significant difference in the cumulative incidence function of pneumonitis between the two groups (p = 0.868). The adjusted subdistribution HR for the incidence of pneumonitis was 1.08 (95% CI: 0.74-1.57). Age (≥ 65 years) (HR: 1.86, 95% CI: 1.11-3.10) and smoking history (HR: 2.04, 95% CI: 1.02-4.11) were associated with developing pneumonitis. CONCLUSION: The risk of developing pneumonitis with ICIs for NSCLC patients with preexisting ILD was similar to that with conventional chemotherapy.