Vascular biology support for the use of bevacizumab in colorectal cancer.

In colorectal cancer, increased expression of the angiogenesis promoter vascular endothelial growth factor correlates with invasiveness, vascular density, metastases, recurrence and prognosis. Bevacizumab is a recombinant humanised monoclonal antibody to vascular endothelial growth factor. In recent clinical trials, bevacizumab has been shown to prolong the time to disease progression and the survival of patients with colorectal cancer. In six patients with adenocarcinoma of the rectum, bevacizumab decreased tumour blood perfusion and volume, interstitial fluid pressure, the number of circulating endothelial cells and fluorodeoxyglucose uptake. Surgical specimens showed a marked response in all six patients with only microscopic disease in five of the patients. These effects of bevacizumab on the vascular biology of tumours probably underlie the progression and survival benefits observed in clinical trials of colorectal cancer.