Furthermore, while one may make inferences regarding the applicability of these observations to anti-VEGF therapy using preclinical data (Huang et al, 2004; Mancuso et al, 2006) and clinical data from other tumours (Willett et al, 2004), only serial biopsies of brain metastases from patients receiving bevacizumab will provide a definitive answer. This evidence concerns the gene VEGFA and neoplasm.