Hypoxia and the radiation response of tumors

The effect of hypoxia on the in vivo radiation response of tumors is demonstrated both for the measurement of cell survival and growth delay following treatment. Results using these endpoints for the KHT Sarcoma are then presented to demonstrate the effect of various parameters which are expected to control tumor oxygenation: blood flow, blood pO2, blood oxygen carrying capacity and tissue consumption of oxygen. Intrinsic blood flow does not correlate with the level of hypoxia in the tumor, but acute reductions in blood flow do result in decreases in tumor oxygenation. Changing the blood PaO2 or the oxygen carrying capacity change the level of hypoxia as predicted, but only certain aspects have been studied. The intricate feedback mechanism which controls normal tissue oxygenation and compensates for any deficiencies cannot be assumed to work effectively in tumors.