Life-threatening pneumonitis after first-line treatment with osimertinib for primary T790M mutated non-small cell lung cancer.

Epithelial growth factor receptor (EGFR) directed tyrosine kinase inhibitor (TKI) treatment is the standard approach in patients with advanced, EGFR-mutated non-small cell lung cancer (NSCLC). Although benefit/risk ratio is favorable for these TKI and side effects are manageable in the vast majority of patients, severe and even life-threatening side effects have been reported. TKI-induced interstitial lung disease (ILD) has been reported for single cases in modest severity, predominantly in EGFR-TKI pretreated patients. Here, we report a case of successful stabilization of a life-threatening ILD in a de novo T790M mutated NSCLC during first-line treatment with osimertinib. As osimertinib will be used more often in many EGFR-positive NSCLC patients in the future, this potentially life-threatening side effect should receive special attention, especially in first-line treatment.