Local Tumor Hyperthermia in the 1990s

Abstract

There is compelling evidence that heat alone is tumoricidal and enhances efficacy of radiation therapy and cytotoxicity of many drugs. However, it is almost certain that during the next decade, heat will be used primarily as an adjuvant to surgery, radiation and chemotherapy rather than alone as the first line of treatment. It is also known that the threshold of thermal damage for normal tissues is not significantly different from that for most tumors, and there is increasing evidence that in normal tissues as in tumors the damage threshold is lower for heat plus drugs and/or radiation than for heat, drugs or radiation alone. For example, in biopsies obtained from the normal liver tissue overlying a tumor in a patient with localized, metastatic liver carcinoma, it was found that whereas heat at 42°C for 20 min., before initiation of chemotherapy with 5Fluorouracil, caused only dilatation and engorgement of capillaries, when the liver was heated in presence of the drug extensive hemorrhages in the parenchyma were observed. Similar toxicity was observed in other tissues such as the kidney. However, it is now generally recognized that to achieve tumor control it is the proliferative and infiltrative tumor margin which must be heated to therapeutic temperature. Therefore to keep normal tissue toxicity at an acceptable level, tumor bed tissues and any critical normal tissues must remain at a lower temperature. Thus, it is important that heating devices must heat most of the tumor, specially its edge, and least of the normal tissue.