Hyperthermia therapy

Hyperthermia therapy
Intervention
Whole-body suit used in hyperthermia therapy.
ICD-10-PCS	[1]
ICD-9-CM	93.35, 99.85
MeSH	D006979
OPS-301 code	8-60
[]

Hyperthermia therapy is a type of medical treatment in which body tissue is exposed to higher temperatures. Hyperthermia uses higher temperatures than diathermy, which is the deep heating of body tissue for relaxation or physical therapy. Techniques that bring local tissues to quite high temperatures, such as radio frequency ablation, are also not usually included in "hyperthermia." When combined with radiation therapy, it is called thermoradiotherapy.

Hyperthermia is defined as supra-normal body temperatures. There is no consensus as to what is the safest or most effective target temperature for the whole body. During treatment the body temperature reaches a level between 39.5 and 40.5 °C (103.1 and 104.9 °F). However, other researchers define hyperthermia between 41.8–42 °C (107.2–107.6 °F) (Europe, USA) to near 43–44 °C (109–111 °F) (Japan, Russia).

Hyperthermia can kill cells directly, but its more important use is in combination with other treatments for cancer. Hyperthermia increases blood flow to the warmed area, perhaps doubling perfusion in tumors, while increasing perfusion in normal tissue by ten times or even more. This enhances the delivery of medications. Hyperthermia also increases oxygen delivery to the area, which may make radiation more likely to damage and kill cells, as well as preventing cells from repairing the damage induced during the radiation session.

Cancerous cells are not inherently more susceptible to the effects of heat. When compared in in vitro studies, normal cells and cancer cells show the same responses to heat. However, the vascular disorganization of a solid tumor results in an unfavorable microenvironment inside tumors. Consequently, the tumor cells are already stressed by low oxygen, higher than normal acid concentrations, and insufficient nutrients, and are thus significantly less able to tolerate the added stress of heat than a healthy cell in normal tissue.

Mild hyperthermia, which provides temperatures equal to that of a naturally high fever, may stimulate natural immunological attacks against the tumor. However it is also induces a natural physiological response called thermotolerance, which tends to protect the treated tumor.

Moderate hyperthermia, which heats cells in the range of 40 to 42 °C (104 to 108 °F), damages cells directly, in addition to making the cells radiosensitive and increasing the pore size to improve delivery of large-molecule chemotherapeutic and immunotherapeutic agents (molecular weight greater than 1,000 Daltons), such as monoclonal antibodies and liposome-encapsulated drugs. Cellular uptake of certain small molecule drugs is also increased.