The issues surrounding tumor oxygenation and radiotherapy used to be simple. Hypoxic
cells are radioresistant and are present in a large proportion of human solid tumors; in
addition, overall tumor oxygenation (as determined by a commercially available oxygen
electrode, commonly referred to as the Eppendorf electrode) correlates with response to
radiotherapy. Because of its correlations with clinical outcomes (particularly in head-and-
neck tumors), the Eppendorf electrode has become “the gold standard” against which all …