Changes in tumor tissue oxygenation during microwave hyperthermia: clinical relevance.

As previously described (Bicher 1981) TpO2 and blood flow increase in tumor as temperature increases until 41 degrees C and decrease thereafter (microcirculation "breaking point"). In the present clinical study using O2 microelectrodes this response was reproduced in over 54 treatment sessions. However, it was found that as treatment progresses (patients are treated for one hour 10 times, twice weekly, and concomitantly receive 4000 rads of ionizing radiation) the initial increase of blood flow and TpO2 is reduced and there is immediate decrease in tissue oxygenation. A correlation between microvascular tumor physiological changes and tumor treatment responses is being developed.