Over-expression of vascular endothelial growth factor after preoperative radiation therapy for rectal cancer.

Vascular endothelial growth factor expression before and after preoperative radiation therapy was examined in 16 stage III rectal carcinoma patients. The biopsied tissues before preoperative radiation therapy and the tissues at operation were immunohistochemically stained. Four cases were negative for VEGF expression before radiation, but the other 12 cases were positive, with 4 cases showing strong immunoreactivity. After radiation, all except 1 case showed VEGF positive patterns, in which 14 cases demonstrated strong staining. In 12 cases, VEGF expression became higher after radiation therapy than before, as compared to the only 1 case that showed lower expression than before.