Rapid Plasma Genotyping For Early Initiation Of Erlotinib In EGFR Mutant Lung Cancer

Inclusion Criteria: * Histologically or cytologically confirmed metastatic NSCLC including recurrent disease * EGFR genotype must not be known. However, pending EGFR tumor genotyping is allowed. --Participants with positive or pending EGFR mutation on plasma genotyping performed at the central lab are eligible for enrollment, and will not need to repeat initial plasma genotyping on study. * Tissue must be available for genotyping or biopsy planned to obtain tissue for genotyping. Biopsy requirement may be waived if not technically feasible and plasma genotyping reveals an eligible EGFR mutation (exon 19 del/L858R). Determination of technical feasibility must be made independently of plasma genotyping results. * Participants must possess at least two of the following clinical characteristics which enrich for EGFR mutations: * smoked less than 10 pack years * Asian race. * Adenocarcinoma (including adenosquamous carcinoma) on histology or cytology. * Participants must have measurable disease with at least one lesion that can be accurately measured in longest dimension as \>2 cm with conventional imaging techniques or \>1 cm with a spiral CT scan per RECIST v1.1. * Participants must have progressive, advanced cancer as defined by one of the following: * Newly diagnosed, untreated advanced disease * Newly diagnosed, untreated metastatic recurrence of earlier stage disease (previous treatment of early stage disease allowed). * Clinical determination of progressive disease on previous systemic therapy as evidenced by plan to change treatment. Any number of prior therapies are acceptable excluding previous EGFR kinase inhibitors. * Age 18 years or older. * ECOG performance status 0-2. * Participant must be able to understand and give consent to participate in the study. * Patient must be a candidate for systemic therapy with erlotinib based on clinical assessment. Patients must meet the following criteria before beginning therapy (Note: these are not required for initial study enrollment and plasma genotyping): * ECOG performance status of 0-2 * Platelets \>75 * AST \& ALT \< 3x the upper limit of normal * Creatinine clearance \> 30 mL/min by Cockroft-Gault * No other contraindication to erlotinib * Female participants of child-bearing age must agree to use adequate contraception (hormonal, barrier or abstinence) for the duration of the study while receiving erlotinib and undergo a pregnancy test. Any evidence or suspicion of pregnancy should be reported to the treating physician immediately. * Male participants must agree to use adequate contraception for the duration of the study while receiving erlotinib Exclusion Criteria: * Participants must not have had chemotherapy within the past 10 days. * Participants must not have had prior treatment with an EGFR kinase inhibitor, EGFR directed therapy or investigational agent. * Participants must not have residual adverse events from previous therapy greater than CTCAE v4.0 grade 2 at the time of registration. * Participants must not have symptomatic brain metastases or brain metastases requiring steroids. Asymptomatic brain metastases not requiring steroids are acceptable. * Participant must not have a history of allergy to erlotinib. * Second primary cancer which is active and requiring treatment. * Participants must not be pregnant or breastfeeding