 The patients will receive standard treatment and follow up. Standard 1st line treatment for patients with disseminated EGFR M disease is erlotinib. Standard follow up during this treatment is blood testing and clinical evaluation every 6th week and a CT scan evaluated by the RECIST criteria every 12th week. Additional tests are ordered on clinical indication. A biopsy and blood sample will be retrieved before treatment with is initiated. The patient will be monitored prospectively with blood samples 2x10 ml EDTA tubes every 3rd-6th week both during erlotinib treatment, subsequent lines of treatment and treatment intermissions. The blood samples will be transported to the Department of Clinical Biochemistry, Aarhus University Hospital where it will be analyzed for subtypes of EGFR M both sensitizing mutations and mutations known to drive resistance to erlotinib treatment. Analyses are performed using the COBAS 4800 light cycler. In the event of occurring resistance mutations or unexpected increase in quantity of sensitizing mutations clinical action will be taken; initially in the form of additional scans searching for signs of disease progression. Clinical data will be retrieved from the patients medical journal. These data include TNM status, histology, treatment modality and patient characteristics gender, age, smoking status and performance status Patients are followed until death or at least 24 months after inclusion. 