<qa>  What is an important surrogate marker of atherosclerotic activity?Several cytotoxic regimens have been shown to cause endothelial cell damage and vascular toxicity by various mechanisms. Thus, anthracyclines and taxanes which forms the cornerstone of breast cancer treatment together with cytotoxics as alkylating agents, bleomycin, vinca alkaloids and antimetabolites have been associated with endothelial cell apoptosis, oxidative stress, inflammation, coagulation disordersthrombotic state, endothelial cell proliferation-migration, effects on VEGF, and impaired endothelial-dependent vasodilation in vitro and in vivo, although the exact mechanisms are not known. Changes in endothelial function hasten the development of micro- and macro-angiopathy and endothelial dysfunction is an important surrogate marker of atherosclerotic activity. Endothelial dysfunction has been implicated in the pathogenesis and clinical course of all known cardiovascular diseases and is associated with future risk of adverse cardiovascular events. 