Patients undergo tumor tissue and blood sample collection periodically for pharmacological and biological studies. Samples are analyzed for concentrations of erlotinib hydrochloride and trough serum levels of sirolimus via HPLC, EGFR, EGFRvIII, PTEN and the phospho-specific antibodies associated with the MAPK and PI3K pathways via IHC, and EGFRvIII and sequencing of EGFR, PTEN and other critical genes via PCR, gene expression, and SNP analysis. Germline DNA will also be used to distinguish polymorphisms from somatic mutations in gene sequenced.