The association between interstitial lung abnormalities (ILA) and various conditions and diseases, including drug-related pneumonitis (DRP), has been reported. However, the association of the presence of ILA with developing DRP in patients undergoing cytotoxic agent-based chemotherapy, one of the standard treatments for malignancies, remains unclear. This warrants urgent investigation.

We included consecutive patients diagnosed with malignancy and treated with cytotoxic agents with/without immune checkpoint inhibitors (ICIs). We used Gray's method and multivariate Fine-Gray sub-distribution hazards analysis to evaluate the cumulative incidence of DRP (common terminology criteria for adverse events grade of ≥3) and the association between ILA and DRP development, respectively.

Among 786 patients, 58 (7.3 %) demonstrated ILA. Patients with ILA were older, predominantly male, and reported a higher smoking history compared to those without ILA. The 90-day cumulative incidence of cytotoxic agent-induced DRP with/without ICIs was significantly higher in patients with ILA than in those without ILA (6.0 % vs. 1.2 %, p = 0.006). Multivariate analysis, adjusted for age, sex, and smoking history, revealed that ILA was associated with an increased risk of developing DRP due to cytotoxic agents with/without ICIs (hazard ratio [HR] 3.11, 95 % confidence interval [CI]: 1.06–9.14, p = 0.039) and cytotoxic agents alone (HR: 5.53, 95 % CI: 1.55–19.7, p = 0.008).

The presence of ILA is associated with an increased risk of developing DRP in patients undergoing cytotoxic agent-based chemotherapy. Therefore, evaluating the presence of ILA before determining chemotherapy regimens that include cytotoxic agents is recommended.