Impact of localized microwave hyperthermia on the oxygenation status of malignant tumors.

Upon heating at 40 degrees C for 30 minutes, the oxygenation of the tumor tissue significantly improved as compared with control conditions at 35 degrees C. In contradistinction to this, the tumor oxygenation significantly decreased directly after 43 degrees C- hyperthermia. A further temperature rise to 45 degrees C caused the oxygenation to drastically drop due to an almost complete cessation of nutritive blood flow. The changes in tumor oxygenation during hyperthermia seem to be predominatly mediated through changes in tumor blood flow, which showed the same directional changes.