Effect of irradiation on tumor microvascular permeability to macromolecules

In C3H mouse Gardner lymphosarcoma, we have demonstrated an increase in the extravascular albumin space 48 hours after delivering 3,000 rads of irradiation. This observation has implications for organ radiobiology in that the microvascular effect could alter radiation response in tumors. This effect may be time dependent and thus may be an extremely important consideration in dose fractionation which is not necessarily dependent on tumor cell cytokinetics. The second ramification of this observation concerns the effect of irradiation on radiotracer techniques designed to identify tumors; following irradiation, an increased macromolecular transport into the interstitial space of a tumor would be anticipated to cause increased accumulation of scanning agents which are bound to protein (e.g., gallium).