Human tumour pH changes following hyperthermia and radiation therapy.

Measurement of human tumour pH was performed during treatment with whole-body hyperthermia (WBHT) at 41.8 degrees C, and prior to and following a series of combined local hyperthermia (LHT) and radiotherapy treatments. During WBHT no changes were seen in the 11 tumour measurements performed during heating, 'plateau' and cooling phases of treatment. Tumour pH rose significantly in 24 tumours in which paired determinations were performed prior to and following local therapy (mean rise, 0.23 pH units), while the 11 subcutaneous controls, measured in a non-treated area, remained unchanged. The lack of change in tumour pH during WBHT is probably related to the moderate treatment temperature (42 degrees C or less), whereas the rise seen following local therapy is probably the result of changes in tissue oxygenation and blood flow following therapy. These changes may have implications to the treatment of malignant disease.