Benefit of switching to firmonertinib following almonertinib-induced interstitial pneumonitis in a patient with advanced non-small-cell lung cancer: a case report.

Almonertinib, a representative epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), is the first-line standard treatment for EGFR-mutant advanced non-small-cell lung cancer; however, it may induce drug-related interstitial lung disease (ILD). This case report presents a 67-year-old female with advanced lung adenocarcinoma, who was diagnosed with an EGFR exon 19 deletion mutation. After 2 months of first-line almonertinib treatment (110 mg/day), a PR was achieved; however, progressive respiratory distress emerged. Chest computed tomography revealed ground-glass opacities accompanied by grid-like changes in both lungs, leading to a diagnosis of EGFR-TKI-related ILD (grade 2). Following glucocorticoid treatment and medication discontinuation, the lung lesions improved. Given the persistent tumor activity, the patient was switched to firmonertinib (80 mg/day) for targeted therapy. This switch did not lead to a recurrence of ILD symptoms, with a progression-free survival exceeding 5 months and good tolerability. This suggests that for patients with ILD associated with almonertinib and firmonertinib may serve as an effective and safe alternative. Closely monitoring ILD in clinical practice and promptly switching to similar drugs may avoid chemotherapy intervention and optimize treatment strategies. This case marks the first report of clinical experience achieving sustained remission by switching to a similar drug, firmonertinib, in patients with ILD related to almonertinib.