Patients undergo blood sample collection at baseline, in weeks 2, 4, 6, and 10, every 4 weeks until disease progression, and then at 4 weeks after disease progression. Blood samples are assessed for circulating endothelial progenitor cell levels by flow cytometry and VEGF, VEGF-C, VEGFR-2, and VEGFR-3 levels by ELISA immunoassays.