since their are much much more blood vessel formation in tumor than normal ones, there will be more
VEGF than normal tissue. Avatin is an anti-
VEGF antibody, will bind to VEGF, destroy the function of VEGF, no more blood vessel will be formed, starve tumor cells to death. But right operation, there will be more blood vessel formation too, it is just one condition which is not suitable for Avastin. Go to Genetech website to find more info.