Osimertinib (AZD9291) in First-line Locally Advanced or Metastatic NSCLC Patients With EGFR and EGFR T790M

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.