How best to interpret measures of levels of oxygen in tissues to make them effective clinical tools for care of patients with cancer and other oxygen‐dependent pathologies

It is well understood that the level of molecular oxygen (O(2)) in tissue is a very important factor impacting both physiology and pathological processes as well as responsiveness to some treatments. Data on O(2) in tissue could be effectively utilized to enhance precision medicine. However, the nature of the data that can be obtained using existing clinically applicable techniques is often misunderstood, and this can confound the effective use of the information. Attempts to make clinical measurements of O(2) in tissues will inevitably provide data that are aggregated over time and space and therefore will not fully represent the inherent heterogeneity of O(2) in tissues. Additionally, the nature of existing techniques to measure O(2) may result in uneven sampling of the volume of interest and therefore may not provide accurate information on the “average” O(2) in the measured volume. By recognizing the potential limitations of the O(2) measurements, one can focus on the important and useful information that can be obtained from these techniques. The most valuable clinical characterizations of oxygen are likely to be derived from a series of measurements that provide data about factors that can change levels of O(2), which then can be exploited both diagnostically and therapeutically. The clinical utility of such data ultimately needs to be verified by careful studies of outcomes related to the measured changes in levels of O(2).