Circulating Plasma Biomarkers for TSU-68, an Oral Antiangiogenic Agent, in Patients with Metastatic Breast Cancer

PURPOSE This study analyzed the role of plasma biomarkers for TSU-68 in a previous phase II trial comparing TSU-68 plus docetaxel and docetaxel alone in patients with metastatic breast cancer. MATERIALS AND METHODS A total of 77 patients were eligible for this study (38 in the TSU-68 plus docetaxel arm and 39 in the docetaxel alone arm). Blood samples were collected prior to the start of each cycle, and vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF)-AA, -AB, -BB, fibroblast growth factor, M30, C-reactive protein (CRP), and interleukin 6 (IL-6) levels were measured using enzyme linked immunosorbent assay. The primary endpoint was progression-free survival (PFS). RESULTS In patients with baseline PDGF-AA ≥ median, median PFS was significantly worse in the TSU-68 plus docetaxel group than in the docetaxel alone group (5.4 months vs. 13.7 months, p=0.049), while a trend toward a PFS benefit was observed in those with baseline PDGF-AA < median (9.7 months vs. 4.0 months, p=0.18; p for interaction=0.03). In the TSU-68 plus docetaxel group, PFS showed significant association with fold changes in CRP (p=0.001), IL-6 (p < .001), PDGF-BB (p=0.02), and VEGF (p=0.047) following the first treatment cycle. CONCLUSION Baseline PDGF-AA levels and dynamics of VEGF, PDGF-BB, CRP, and IL-6 levels were predictive for the efficacy of TSU-68.