PATTERN OF RESPONSE TO INTERSTITIAL HYPERTHERMIA AND BRACHYTHERAPY FOR MALIGNANT INTRACRANIAL TUMOR - A CT ANALYSIS

Interstitial microwave hyperthermia in combination with iridium-192 br achytherapy has been administered to 23 cases of malignant brain tumou rs in a phase one clinical trial to assess the feasibility and safety of this treatment. In order to quantify the acute and long-term respon se of tumour and surrounding brain to this treatment, a morphometric c omputed tomography scan analysis was performed in 18 evaluable patient s. Volumes defined by the outer margin of the contrast-enhancing rim, by the hypodense necrotic region within the enhancing rim and by the s urrounding hypodensity region were calculated from computer measuremen ts. Hyperthermia equipment performance (HEP) was calculated for the ev aluation of heating. After the treatments, the volume of the inner hyp odensity region decreased in seven patients and the volume increased i n 11 patients. In five patients, the outer margin of the contrast-enha ncing lesion showed an initial increase in volume followed by a decrea se and in these patients higher HEP and longer survival were observed significantly. The volume of the surrounding hypodensity region varied following treatments, but in most instances, the region subsequently increased in the interval immediately prior to death. Contribution of heat effect to these changes are discussed and the significance of agg ressive heating, which provides transient opening of blood brain barri er, is shown.