Patients undergo tumor tissue and blood sample collection at baseline and periodically during study for biomarker correlative studies. Archived tumor tissue samples, if available, are analyzed for Bcl-2 family protein expression (e.g., Bcl-2, Bcl-xL, MCl-1, Bax, Bak, and BH3 domain for BH3 members only) and 06-methylguanine-DNA-methyltransferase (MGMT) gene methylation status. Blood samples are analyzed for apoptotic protein levels (Bcl-2) by enzyme-linked immunosorbent assay.