Oxygenation of human tumors.

The objective of this article is to summarize current knowledge of oxygen supply to human tumors and of tumor tissue oxygenation, parameters which go hand in hand, and in turn critically determine the cellular metabolic microenvironment of human malignancies. A compilation of available data on these factors is presented. Though data on human tumors in situ are scarce and there may be significant errors associated with the technique used for measurements, experimental evidence is provided for the existence of a compromised and anisotropic oxygen supply to many tumor cells. Comparable to experimental rodent tumors, O2-depleted areas develop in many human malignancies which coincide with nutrient and energy deprivation, and with a hostile metabolic microenvironment. Significant variations in these relevant parameters have to be expected between different locations within the same tumor, at the same location at different times, and between individual tumors of the same grading and staging. Therefore, evaluation of the oxygenation status in individual tumors before therapy might be most beneficial for designing specifically tailored treatment protocols for individual subjects in order to improve tumor response to treatment.