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Hyperthermia (thermal therapy), the generation of temperatures greater than physiologic fever range (above 41.5°C [106.7°F]), has been used for many years to destroy tumors in human can-cers. Malignant cells may be more sensitive than normal cells to the harmful effects of high temperatures for several reasons. Ma-lignant cells lack the repair mechanisms necessary to repair cell damage by elevated temperatures. Most tumor cells lack an ade-quate blood supply to provide needed oxygen during periods of increased cellular demand, such as during hyperthermia. Can-cerous tumors lack blood vessels of adequate size for dissipation of heat. In addition, the body’s immune system may be indirectly stimulated when hyperthermia is used.
Hyperthermia is most effective when combined with radiation therapy, chemotherapy, or biologic therapy. Hyperthermia and radiation therapy are thought to work well together because hy-poxic tumor cells and cells in the S phase of the cell cycle are moresensitive to heat than radiation; the addition of heat damages tumor cells so that they cannot repair themselves after radiation therapy. Hyperthermia is thought to alter cellular membrane per-meability when used with chemotherapy, allowing for an in-creased uptake of the chemotherapeutic agent. Hyperthermia may enhance function of immune system cells, such as macrophages and T cells, which are stimulated by many biologic agents.
Heat can be produced by using radiowaves, ultrasound, micro-waves, magnetic waves, hot-water baths, or even hot-wax im-mersions. Hyperthermia may be local or regional, or it may include the whole body. Local or regional hyperthermia may be delivered to a cancerous extremity (for malignant melanoma) by regional perfusion, in which the affected extremity is isolated by a tourni-quet and an extracorporeal circulator heats the blood flowing through the affected part. Hyperthermia probes may also be in-serted around a tumor in a local area and attached to a heat source during treatment. Chemotherapeutic agents, such as melphalan (Alkeran), may also be heated and instilled into the region’s cir-culating blood. Local or regional hyperthermia may also include infusion of heated solutions into cancerous body organs. Whole-body hyperthermia to treat disseminated disease may be achieved by extracorporeal circulation, immersion of patients in heated water or paraffin, or enclosure in heated suits.
Side effects of hyperthermic treatments include skin burns and tissue damage, fatigue, hypotension, peripheral neuropathies, thrombophlebitis, nausea, vomiting, diarrhea, and electrolyte im-balances. Resistance to hyperthermia may develop during the treatment because cells adapt to repeated thermal insult. Research into the effectiveness of hyperthermia, methods of delivery, and side effects is ongoing.
Although hyperthermia has been used for many years, many pa-tients and their families are unfamiliar with this cancer treatment. Consequently, they need explanations about the procedure, its goals, and its effects. The patient is assessed for adverse effects, and efforts are made to reduce their occurrence and severity. Local skin care at the site of the implanted hyperthermic probes is also required.
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