Measurement of tumor oxygenation: in vivo comparison of a luminescence fiber-optic sensor and a polarographic electrode in the p22 tumor

Hypoxia is important in tumor biology and therapy. This study compared the novel luminescence fiber-optic OxyLite sensor with the Eppendorf polarographic electrode in measuring tumor oxygenation. Using the relatively well-oxygenated P22 tumor, oxygen measurements were made with both instruments in the same individual tumors. In 24 air-breathing animals, pooled electrode pO(2) readings lay in a range over twice that of sensor pO(2(5min)) values (-3.2 to 80 mm Hg and -0.1 to 34.8 mm Hg, respectively). However, there was no significant difference between the means +/- 2 SE of the median pO(2) values recorded by each instrument (11.0 +/- 3.3 and 8.1 +/- 1.9 mm Hg, for the electrode and sensor respectively, P = 0.07). In a group of 12 animals treated with carbon monoxide inhalation to induce tumor hypoxia, there was a small but significant difference between the means +/- 2 SE of the median pO(2) values reported by the electrode and sensor (1.7 +/- 0.9 and 2.9 +/- 0.7 mm Hg, respectively, P = 0.009). A variable degree of disparity was seen on comparison of pairs of median pO(2) values from individual tumors in both air-breathing and carbon monoxide-breathing animals. Despite the differences between the sets of readings made with each instrument from individual tumors, we have shown that the two instruments provide comparable assessments of tumor oxygenation in groups of tumors, over the range of median pO(2) values of 0.6 to 28.1 mm Hg.