Evaluation of oxygen diffusion distances in human breast cancer xenografts using tumor-specific in vivo data: role of various mechanisms in the development of tumor hypoxia.

Oxygen diffusion distances in human breast cancer xenografts are computed considering cell line-specific in vivo data. By introducing variations into a set of experimental data characterizing a "standard" situation, the impacts of various tumor-specific or systemic mechanisms are studied. Evidence is given that radioresistance may develop at intercapillary distances above 100 micron. If intercapillary distances exceed 140 micron, hypoxia is present at the arterial end of microvessels already. Hypoxia evidenced under "standard" conditions is distinctly aggravated by reduction of microvascular blood flow, increased arterio-venous shunt perfusion, reduced red blood cell flux, elongation of tumor microvessels, anemia or arterial hypoxemia. Hypoxic tissue fractions calculated for these various conditions are found to be in accordance with the proportion of tumor tissue Po2-readings at 0-1 mmHg.