Tumor Oxygenation Status: Facts and Fallacies.

In this chapter we allude to a series of facts and fallacies often encountered in the description of tumor hypoxia, a relevant trait of the tumor microenvironment and a paramount driver of tumor aggressiveness and treatment resistance. The critical role of diffusion distances, terminological inconsistencies considering O ₂ partial pressures vs. O ₂ concentrations and with it the use of inept units, the impact of O ₂ depletion on proliferation and cell viability, the switch in the Warburg dogma , the distribution of hypoxic subvolumes within a tumor, the involvement of O ₂ diffusion shunts in the development of chronic hypoxia, and the role of endogenous biomarkers as surrogates for the assessment of hypoxia are discussed in more detail. Special emphasis is put on the clinical relevance of these misconceptions and misinterpretations and their impact on the assessment of hypoxia as well as hypoxia-targeted treatment planning.