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

Abstract 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.