Activity of osimeRTInib in non-small-cell lung Cancer with UNcommon epidermal growth factor receptor mutations: retrospective Observational multicenter study (ARTICUNO)

Background: Osimertinib represents the standard of care for the treatment of advanced non-small-cell lung cancer (NSCLC) harboring classical epidermal growth factor receptor (EGFR) mutations, constituting 80%-90% of all EGFR alterations. In the remaining cases, an assorted group of uncommon alterations of EGFR (uEGFR) can be detected, which confer variable sensitivity to previous generations of EGFR inhibitors, overall with lower therapeutic activity. Data on osimertinib in this setting are limited and strongly warranted. Patients and methods: The ARTICUNO study retrospectively evaluated data on osimertinib activity from patients with advanced NSCLC harboring uEGFR treated in 21 clinical centers between August 2017 and March 2023. Data analysis was carried out with a descriptive aim. Investigators collected response data according to RECIST version 1.1 criteria. The median duration of response, progression-free survival (mPFS), and overall survival were estimated by the Kaplan–Meier method. Results: Eighty-six patients harboring uEGFR and treated with osimertinib were identified. Patients with ‘major’ uEGFR, that is, G719X, L861X, and S768I mutations (n = 51), had an overall response rate (ORR) and mPFS of 50% and 9 months, respectively. Variable outcomes were registered in cases with rarer ‘minor’ mutations (n = 27), with ORR and mPFS of 31% and 4 months, respectively. Among seven patients with exon 20 insertions, ORR was 14%, while the best outcome was registered among patients with compound mutations including at least one classical EGFR mutation (n = 13). Thirty patients presented brain metastases (BMs) and intracranial ORR and mPFS were 58% and 9 months, respectively. Amplification of EGFR or MET, TP53 mutations, and EGFR E709K emerged after osimertinib failure in a dataset of 18 patients with available rebiopsy. Conclusion: The ARTICUNO study confirms the activity of osimertinib in patients with uEGFR, especially in those with compound uncommon–common mutations, or major uEGFR, even in the presence of BMs. Alterations at the E709 residue of EGFR are associated with resistance to osimertinib.