Anti-VEGF therapy: the search for clinical biomarkers

Despite the large diffusion and rapid development of anti-VEGF therapy in clinical practice and in contrast to the consolidated evidence with imatinib and trastuzumab that demonstrated a direct correlation between pre-treatment target expression and drug activity, it is very difficult, at present, to identify validated and useful biomarkers to monitor the efficacy of these compounds and to appropriately select patients most likely to benefit from such treatments. However, emerging data suggest that this is not presently feasible for antiangiogenic drugs. Although tumoral and/or circulating VEGF levels have been associated with tumor progression and/or poor prognosis, to date, there is no validated evidence suggesting their role as potential predictive biomarkers of response to anti-VEGF therapy. Recently, many studies have documented promising results with the evaluation of circulating endothelial cells and/or progenitors, and the use of several imaging techniques, such as dynamic contrast-enhanced MRI, PET, dynamic CT scan and functional ultrasound. These preliminary data need a validation in larger prospective trials.