Low-dose, short-course sunitinib may normalize tumor vasculature and improve tumor blood flow to enhance chemotherapy efficacy in breast cancers.

1064 Background: Small molecule VEGFR inhibitors (VEGFR-I) have failed to improve outcome with chemotherapy in most solid tumors. Continuous administration of a potent VEGFR-I may destroy vasculature and impede drug delivery; in contrast, low-dose, short-course VEGFR-I before chemotherapy may normalize tumor vasculature and enhance drug delivery. Methods: We conducted a phase Ib followed by phase II randomized study in patients with measurable primary breast tumors using low-dose sunitinib (Su) for 1 week prior to doxorubicin/cyclophosphamide (AC) and measured tumor blood flow with DCE-MRI and microvessel density and pericyte recoverage with CD31 and α-smooth muscle actin (SMA) staining on tumor biopsies, at baseline, after 1 week of Su, and 2 weeks after cycle 1 AC. Patients in phase Ib received 12.5-25mg Su prior to AC; in phase II, patients were randomized to AC+/-12.5mg Su. Results: 21 patients have been enrolled, including 3 patients on 25mg Su+AC, 11 on 12.5mg Su+AC, and 7 on AC alone. After 1 week ...