The role of imaging in the clinical development of antiangiogenic agents.

Early clinical development of novel antiangiogenesis agents is hampered by the fact that classic response end points are unlikely to be relevant and there is a lack of validated surrogate markers of efficacy. Toxicity-based decisions for dose setting and tumor size measurements by standard imaging probably are not be applicable. Because these agents modify a multitude of biologic processes that may cause early measurable effects, there is great interest in developing imaging tests that are sensitive to changes in tissue function. This article discusses the development of such "functional" clinical imaging and attempts to address the questions that are being asked of imaging departments by oncologists and pharmaceutical companies.