Radiotherapy before surgery can reduce the size of some rectal cancers making it possible to remove the tumor without harming the sphincter muscle that closes the rectum and controls bowel movements. When surgeons are able to preserve the sphincter, rectal cancer patients can avoid permanent colostomies. Being able to predict which patients will respond to radiation therapy would help doctors to select those who would benefit most from presurgical treatment.
Researchers at McGill University have found that [levels of VEGF expression](http://www3.interscience.wiley.com/cgi-bin/abstract/112102167/ABSTRACT) are a useful way of predicting whether or not radiotherapy before surgery will reduce rectal tumors. VEGF — vascular endothelial growth factor — is a protein produced by cells, including cancer cells, that encourages the development of nearby blood vessels.
They measured levels of VEGF expression in 59 rectal tumor biopsies taken before radiation treatment. The studied samples were either from tumors that had completely responded to radiation therapy and where cancer was no longer evident to either surgeons or pathologists (CR — complete response) or from tumors that did not shrink during radiation treatment (NR — nonresponsive).
The average VEGF expression in nonresponsive tumors was significantly higher than that of tumors that responded completely to presurgical radiation. Over half of nonresponsive tumors had VEGF levels of 80% of greater. On the other hand, half of complete responders had VEGF levels of less than 10%. Eleven tumors had no reactivity to VEGF at all (0%) and all had responded completely to radiotherapy.
Inti Zlobec, M.Sc. and colleagues in the Department of Pathology at McGill University in Montreal reported the results of their research in the [early online edition of Cancer](http://www3.interscience.wiley.com/cgi-bin/abstract/112102167/ABSTRACT) on October 12, 2005. They wrote,
The results of this study indicate that VEGF assessed immunohistochemically from preirradiation tumor biopsies may be a useful marker of rectal tumor response to preoperative radiotherapy.