Safety and Efficacy of Gefitinib Administration After Osimertinib-Induced Interstitial Lung Disease: A Six-Case Series.

Purpose: Osimertinib, a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, is the standard treatment for patients with non-small cell lung cancer harboring EGFR mutations. Although the frequency of osimertinib-induced interstitial lung disease (osi-ILD) is high, the optimal cancer treatment after osi-ILD has not been established. This time, we focused on the safety and efficacy of gefitinib following osi-ILD. Case Presentation: We experienced six cases (five women and one man; median age: 74 years) in which gefitinib was administered after osi-ILD. All six cases had grade 2 or higher osi-ILD and required steroid treatment. The computed tomography imaging pattern of osi-ILD revealed organizing pneumonia in three cases, diffuse alveolar damage in two cases, and hypersensitivity pneumonia in one case. Eastern Cooperative Oncology Group performance status was 1 in four cases, 2 in one case, and 3 in one case. EGFR mutation status was exon 19 deletion in two cases and exon 21 L858R in four cases. Only one patient experienced recurrence of ILD after receiving gefitinib. The best response to gefitinib was partial response in two cases and stable disease in three cases; one case was not evaluable. The median progression-free survival after treatment with gefitinib was 190 days (95% confidence interval: 33-328). Conclusion: The treatment with gefitinib after the development of osi-ILD was safe and effective. Gefitinib may be a promising option for patients who recovered from severe osi-ILD.