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RESEARCH PRODUCT

Blood Flow and Tissue Oxygenation of Human Tumors: An Update

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It is generally accepted that tumor microcirculation, blood flow, oxygen and nutrient supply, tissue pH distribution, and the bioenergetic status (factors which are usually closely linked and which define the so-called cellular microenvironment) can markedly influence the therapeutic response of malignant tumors. Tumor blood flow is the major determinant for intra-tumor pharmacokinetics and (through modulation of the cellular microenvironment) of pharmacody-namics. The oxygen supply greatly determines the radiosensitivity of the tumors to be treated. The oxygen enhancement ratio, i.e., the ratio of doses with and without oxygen to produce the same biological effect is 2.7 to 3.0. O2 partial pressures (O2 tensions) of 3 to 4 mmHg (i.e., 0.5 to 0.6% O2) result in a sensitivity halfway between radiobiological hypoxia and full oxygenation (Vaupel, 1992).