Clinical outcomes of patients with EGFR-mutated NSCLC developing interstitial lung disease during first-line osimertinib therapy: a sub-analysis of the Reiwa study.

Introduction: Osimertinib-induced interstitial lung disease in untreated EGFR-mutated, advanced non-small cell lung cancer is being reported at a higher rate in Japan than elsewhere. However, data on the interstitial lung disease incidence during first-line osimertinib therapy and the course of lung cancer treatments administered after interstitial lung disease onset in the real-world setting are scarce.

Materials and methods: The present study reviewed the data from the Reiwa study, a multicentric, observational study examining the efficacy and safety of first-line osimertinib therapy in the clinical setting. Patients with EGFR-mutated non-small cell lung cancer who began osimertinib therapy between September 2018 and August 2020 were enrolled and followed until August 2022.

Results: Among 583 patients receiving first-line osimertinib therapy, 75 (12.8%) had interstitial lung disease development, and 18 (3.0%) had at least grade 3 interstitial lung disease. Fifty-nine patients (78%) received some form of treatment following interstitial lung disease onset. An epidermal growth factor receptor-tyrosine kinase inhibitor rechallenge was performed in 31 patients (41%), with 18 (24%) receiving osimertinib again. Interstitial lung disease recurred in five (28%) of these 18 patients, none of 13 patients receiving another type of tyrosine kinase inhibitor, and seven (25%) of 28 patients receiving chemotherapy and/or immune checkpoint inhibitor therapy. The median overall survival after the initial osimertinib therapy was 38.4 months and 12.2 months for patients with interstitial lung disease grade 1-2 and grade 3-4, respectively (hazard ratio: 0.37; 95% confidence interval: 0.20-0.70; P = 0.002).

Conclusion: Patients with interstitial lung disease grade 3-4 had poorer survival during the first-line osimertinib therapy. A substantial risk of interstitial lung disease recurrence was associated with post-osimertinib therapy. Trial registration code: UMIN000038683.