Relevant parameters for describing the oxygenation status of solid tumors.
OBJECTIVE
Several studies using different methods of pO2 measurement have shown that in many tumor entities tissue oxygenation is quite heterogeneous and thus cannot be sufficiently described by a single value. This study presents those distribution parameters which are mandatory to describe the complete oxygenation status of a solid tumor.


METHODS
In determining the oxygenation status different aspects of relevancy have to be taken into account. First, several parameters are necessary to characterize the location, the spread, and the shape of the pO2 distribution from a statistical point of view (statistical parameters). In addition, parameters for the description of the biological relevance of the tumor oxygenation have to be considered (biological parameters). These parameters reflect the role of oxygenation for the metabolic microenvironment and the biological behavior of the tumor as well as the significance under therapeutic and diagnostic aspects. Finally, some parameters are necessary to assess the quality of pO2 measurement itself (quality parameters).


RESULTS
By combining all pO2 readings from one tumor a statistical distribution is obtained, which is in many tumors asymmetrically shifted towards low pO2 values. In order to describe the location, spread, and shape of this distribution the following parameters should be stated: median, mean, 10% and 90% percentile, minimum, maximum and 10 to 90% interpercentile range. For data presentation these values can be combined in a box-whiskers plot. In order to reflect the importance of tumor oxygenation under diagnostic, therapeutic or cell-biological aspects the fraction of pO2 readings < or = 2.5 mm Hg, < or = 5 mm Hg, and < or = 10 mm Hg should be stated. Where negative pO2 readings occur in a study, the fraction of pO2 readings < 0 mm Hg as well as the most negative pO2 value should be presented in order to assess the quality of the pO2 measurement.


CONCLUSIONS
For a comprehensive description of the oxygenation status of solid tumors the following distribution parameters should be stated: median, mean, 10% and 90% percentile, minimum, maximum, 10 to 90% interpercentile range, fraction of pO2 readings < 0 mm Hg, < or = 2.5 mm Hg, < or = 5 mm Hg, and < or = 10 mm Hg as well as the most negative pO2 reading.
Thews
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Institute of Physiology and Pathophysiology, University of Mainz.
Vaupel
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D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D010100:Oxygen / Q000378:metabolism*
D010100:Oxygen