<qa>  What is the purpose of the study?As in ongoing collaborations with the University of Chicago Section of Dermatology, patients in this proposed study will undergo skin biopsies at enrollment and after 2 weeks of cetuximab therapy. The investigators will extract mRNA from the fresh frozen skin specimens and perform microarray studies to test the utility of mRNA expression patterns associated with rash and responsiveness to EOFR inhibitors in currently ongoing investigations at the University of Chicago. Therefore we expect this study: 1 to identify any significant improvement of concurrent cetuximabpemetrexed therapy for second-line treatment of NSCLC over sequential monotherapy, 2 through timely minimally invasive collection of serum and exposed skin, to provide the opportunity to test previously identified biomarkers for individual responsiveness to cetuximab therapy, and 3 to confirm prospectively whether early development of rash on cetuximab treatment predicts responsiveness to either concurrent or sequential therapy. 