Resistance & Activating Mutations Diagnosed Among NSCLC Community Dwelling EGFR Mutation Positive Patients

Inclusion Criteria: * Provision of informed consent prior to any study-specific procedures * Females and males \>/= 18 years * Primary diagnosis of NSCLC with evidence of disease progression during or following treatment with an EGFR tyrosine kinase inhibitor (diagnosis of NSCLC that is confirmed by cytology is acceptable) * Willing to undergo tumor biopsy (e.g., excision, core biopsy, or endoscopic biopsy), preferably of a progressing lesion, and provide blood and urine for biomarker testing * Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2 Exclusion Criteria: * Involvement in the planning and/or conduct of the study * Prior treatment with osimertinib or another T790M directed therapy * Current participation in another clinical study with an investigational product or patients who plan to receive any treatment that is not FDA-approved for EGFR mutation positive NSCLC at any time during the course of this study * Use of any chemotherapeutic agent within 1 week of tissue, plasma, and urine sample collection * For women - currently pregnant or plan to become pregnant during the course of the study: pre-menopausal women of childbearing potential must have a urine or serum pregnancy test performed during the screening/enrollment period and prior to initiating anti-cancer treatment * Judgment by the investigator that the patient should not participate in the study due to the patient being unlikely to comply with study procedures, restrictions, and requirements, such as in the case of severe or uncontrolled systemic disease.