REDUCED OXYGENATION IN A RAT MAMMARY-CARCINOMA AFTER CHEMO-THERAPY ORRADIATION-THERAPY AND REOXYGENATION WITH PERFLUBRON EMULSION CARBOGENBREATHING/

Rat 13672 mammary carcinoma tumors were grown subcutaneously in the hi nd legs of female Fischer 344 rats to a volume of about 1 cm(3). Tumor oxygenation was measured using an Eppendorf PO2 histograph. Tumor oxy gen measurements were made under four conditions: (a) normal air breat hing, (b) carbogen breathing, (c) after intravenous administration of a perflubron emulsion (8 ml/kg) with air breathing and (d) after intra venous administration of a perflubron emulsion (8 ml/kg) with carbogen breathing. Tumor oxygenation was examined without treatment or 24 h a nd 48 h after treatment with cyclophosphamide (300 mg/kg, i.p.) or cis platin (8 mg/kg, i.p.] or after the fifth dose of a daily regimen of 3 -Gy irradiation (5x3 Gy). Under normal air-breathing conditions 49% of the tumor had a PO2 less than or equal to 670 Pa (5 mm Hg). The degre e of hypoxia in the tumors increased after each treatment such that 24 h after treatment 65%-85% of the oxygen readings were less than or eq ual to 670 Pa and 48 h after treatment 60%-74% of the oxygen readings were less than or equal to 670 Pa. Administration of the perflubron em ulsion/carbogen atmosphere increased the oxygen content of the tumors both without treatment and after each of the treatments. A knowledge o f tumor oxygen content over the course of treatment and the ability to increase tumor oxygen should allow for the development of more ration al treatment combinations and better treatment outcomes.