Naïve patients ≥ 18 years of age with histological confirmation of locally advanced or metastatic, non-squamous non-small cell lung cancer (NSCLC) with an activating EGFR mutation and concomitant T790M mutation. Evidence of measurable or evaluable metastatic disease is required.~Primary objective:~To evaluate the efficacy of osimertinib (AZD9291), in terms of the objective response rate in patients with advanced non-squamous NSCLC with EGFR mutations and the EGFR T790M mutation at diagnosis as defined by RECIST 1.1 criteria.~Secondary objectives:~To determine the safety and tolerability profile of osimertinib (AZD9291), measured using the number and severity of AEs entered into the Case Report Form (CRF); chemistry, blood count, vital signs, physical examination, weight, ECG and performance status (S).~To determine other efficacy parameters such as progression-free survival (PFS), overall survival (OS), time to treatment failure (TTF), duration of response (DOR), disease control rate (DCR), and tumor shrinkage (TS).~To correlate the parameters of clinical response efficacy documented with the EGFR mutational status.~To carry out a longitudinal analysis of EGFR mutations (including the T790M mutation) in plasma and serum.~To determine levels of BIM mRNA as well as mRNA levels of other biomarkers related to EGFR TKI response and determine whether they are predictors of treatment response.~To identify mechanisms of acquired resistance to osimertinib (AZD9291); mutations at the site of covalent binding to the drug (C797) or other mutations in tissue or blood.~Type of study: Multicenter, international, single-arm, open-label, non-controlled phase IIa clinical study.~Treatment: Patients will be treated with 1 tablet of osimertinib (AZD9291) 80 mg per os (p.o.) daily.
The primary goal is to evaluate the efficacy of osimertinib (AZD9291), in terms of the objective response rate in patients with advanced non-squamous NSCLC with EGFR mutations and the EGFR T790M mutation at diagnosis as defined by RECIST 1.1 criteria.~Safety and efficacy will also be measured.