Effects of hyperthermia on normal and tumor microenvironment.

The effects of hyperthermia on pH, local blood flow (LBF) and tissue oxygen tension (TpO2) in several normal and tumor tissues were studied. It was found that TpO2, local blood flow and pH are inhomogeneous in tumor tissue. TpO2 is very low in certain areas which also seem deprived of blood flow and are at very low pH. Hyperthermia has a dual effect: at temperatures below 41 degrees C, it increases blood flow and TpO2 while above 41 degrees C, it causes a collapse in blood flow, lower TpO2 and a shift of the tissue pH towards acidosis from the already low pH values found in tumors.