Inclusion Criteria:  Age ≥18 years. ECOG performance status 0-1. Pathologically confirmed diagnosis of Stage IIIB/IV adenocarcinoma of the lung. Have been commenced on first line afatinib 30 mg within 4 weeks of study enrolment. Documented EGFR mutation(s)-positive NSCLC (common mutations: Del19 and L858R) from tumour biopsy material. Results of EGFR mutation test must be available before taking Afatinib. A CT thorax/ abdomen within 4 weeks of study enrolment with at least one measurable lesion according to the Response Evaluation Criteria in Solid Tumours (RECIST) version 1.1. No brain metastases (confirmed by a CT or MRI brain performed within 4 weeks of study enrolment)  Documented adequate organ function before taking Afatinib:  Absolute neutrophil count (ANC) ≥1500/mm3. (ANC >1000/mm3 may be considered in special circumstances such as benign cyclical neutropenia as judged by the Investigator and in discussion with the sponsor-Investigator). Platelet count ≥75,000/mm3. Estimated creatinine clearance using Cockcroft Gault calculation of at least 45 ml/min. Total Bilirubin ≤1.5 times upper limit of (institutional/central) normal (Patients with Gilbert's syndrome total bilirubin must be ≤4 times institutional upper limit of normal). Aspartate amino transferase (AST) or alanine amino transferase (ALT) ≤3 times the upper limit of (institutional/central) normal (ULN) (if related to liver metastases ≤5 times ULN). Archived tissue sample is available. Written informed consent per regulations.  Exclusion Criteria:  Prior chemotherapy for Stage IIIB/IV adenocarcinoma of the lung. Neo-/adjuvant chemotherapy, CT-RT or RT is permitted if it has been elapsed for =12 months prior to disease progression. Prior treatment with EGFR targeting small molecules or antibodies. Major surgery within 4 weeks of study treatment. Brain metastases. Meningeal carcinomatosis. Known pre-existing interstitial lung disease (ILD).  Patients with a significant disease other than lung cancer; a significant disease is defined as a disease which, in the opinion of the investigator, may:  put the patient at risk because of participation in the study influence the results of the study cause concern regarding the patient's ability to participate in the study.