Increase in tumor pO2 by perfluorochemicals and carbogen

The effects of perfluorochemicals (Fluosol-DA) in combination with carbogen (95% O2 and 5% CO2) breathing on the tumor pO2 was investigated. The pO2 in RIF-1 tumors grown in the leg of C3H mice was determined by polarographic method using oxygen microelectrodes with diameters of 50-60 micron. The average and median pO2 in the control RIF-1 tumors was about 13 mm Hg and 6 mm Hg, respectively. Carbogen breathing alone could cause a significant increase in pO2 in some tumors and Fluosol-DA injection (i.v.) alone caused a slight change in tumor pO2. When the animals were treated with both Fluosol-DA injection and carbogen breathing, the pO2 markedly increased in most of the tumors resulting in an average and median tumor pO2 of 80 mm Hg and 60 mm Hg, respectively. Such an increase in tumor pO2 may account for the previous observations by us and others that the response of experimental tumors to radiation could be markedly increased by treating the tumor-bearing animals with carbogen and Fluosol-DA.