Hyperthermia has great potential as an
antineoplastic agent because: (a) it is effective against relatively radioresistant hypoxic cells and cells in S phase; (b) unlike most chemotherapeutic agents, it is effective against poorly vascularized and metabolically quiescent tissues; (c) as a physical agent, its
biological effect is related to the duration and intensity of its application; (d) it seems to have no cumulative toxicity; and (e) it potentiates the effects of both
chemotherapy and ionizing radiation at the cellular level. The use of
hyperthermia for malignant
brain tumors is constrained by a relatively narrow therapeutic index and the considerable thermal sensitivity of normal neural tissue.
Glioblastoma multiforme, by virtue of its low growth fraction and heterogeneous cell populations, seems to be an ideal candidate for
hyperthermia administered as part of a combined modality treatment program. Focal
hyperthermia can be produced by a number of energy sources, including those utilizing ultrasound, microwave, and radiofrequency generators. The clinical safety and feasibility of a miniature microwave radiator/sensor system for direct implantation have been demonstrated. In comparison to normal feline brain, malignant
brain tumors in humans are unable to dissipate heat efficiently.