The effect of tetrathiomolybdate on endothelial progenitor cells in patients at high risk for breast cancer recurrence

1054 Background: Bone marrow-derived endothelial progenitor cells (EPCs) are critical for metastatic progression. Tetrathiomolybdate (TM), an oral copper-depleting compound, inhibits angiogenesis and maintains tumor dormancy. This study explores the effect of TM on EPCs in patients (pts) at high risk for breast cancer recurrence. Methods: This phase II study enrolled pts with stage III, stage IV without evidence of disease (NED) breast cancer, and stage II if triple negative (TN). Only concomitant hormone therapy was allowed. Pts received induction TM 180 mg daily followed by 100 mg daily to maintain ceruloplasmin (Cp) level < 17 mg/dL (target for copper depletion). TM was continued for 24 months (mo), or until relapse or toxicity, with an extension study for additional 24 mo in selected pts. We monitored EPCs (CD45dim/CD133+), Cp, CEA and CA15-3 at baseline (BL) and monthly. EPCs were quantitated from peripheral blood mononuclear cells by flow cytometry. Median BL EPCs was compared to subsequent time poi...