First experience with osimertinib in patients with T790M mutation previously treated with EGFR – TKIs in Croatia.

Abstract

e20518 Background: EGFR T790M mutation is responsible for around 60% cases of resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) in patients who have lung cancer with an activating EGFR mutation. Methods: We administered osimertinib 80 mg once daily in 8 patients with advanced lung cancer who had radiologically documented disease progression after previous treatment with first and second-line EGFR tyrosine kinase inhibitors. Results: We treated 8 patients with osimertinib with stage IV lung adenocarcinoma. Four patients were males and four were females, median age 62 (raging from 54 to 82). Four patients were never smoker, and four were ex-smokers. All patients had initially deletion 19 in EGFR gene and then developed T790M mutation. In all patients T790M was proven from tumor tissue. Majority of patients were ECOG 1. All patients were previously treated with first or second line EGFR TKIs (erlotinib, gefitinib or afatinib) and had radiologically documented disease progression. Three patients were treated with osimertinib in third line setting, 2 in fourth, one in fifth, one in sixth and one even in tenth line setting. Median time to response was 4 weeks (raging from 3 to 7). All 8 patients had partial response (PR) with still no recorded disease progression. Duration of response is from 7 to 46 weeks and still ongoing. No significant side effects were observed. Conclusions: Osimertinib is highly active in patients with lung adenocarcinoma which harbor EGFR T790M mutation who had had disease progression during prior therapy with EGFR tyrosine kinase inhibitors. There were no serious side effects of treatment.