Hyperthermia in general means a body temperature that is higher than normal. High body temperatures are often caused by illness such as fever or heat stroke. But hyperthermia can also refer to heat treatment -- the carefully controlled use of heat for medical purposes. This document focuses on how heat is used to treat cancer.

When cells in the body are exposed to higher than normal temperatures, changes take place inside the cells. These changes can make the cells more likely to be affected by radiation therapy or chemotherapy. Very high temperatures can kill cancer cells outright.

The idea of using heat to treat cancer has been around for some time, but early attempts to treat cancer with heat had mixed results. And it was hard to maintain the right temperature in the right area while limiting the effects on other parts of the body. Today, newer tools allow better control and more precise delivery of heat, and hyperthermia is being studied for use against many types of cancer.

How can hyperthermia be used to treat cancer?

There are 2 main ways in which hyperthermia can be used:

• Very high temperatures can be used to destroy a small area of cells, such as a tumor. This is commonly referred to as local hyperthermia or thermal ablation.

• The temperature of a part of the body (or of the whole body) can be raised to a higher than normal level. Although it isn't hot enough to kill the cells directly, it can allow other types of cancer treatments such as radiation therapy, immunotherapy, or chemotherapy to work better. This is known as either regional hyperthermia or whole body hyperthermia.

Local hyperthermia

Local hyperthermia (or thermal ablation) is used to heat a very small area, such as a tumor. It involves creating very high temperatures that destroy (ablate) the cells that are heated. Radio waves, microwaves, ultrasound waves, or other forms of energy can be used to heat the area. The heat may be applied using different methods:

• External: High energy waves are aimed at a tumor near the body surface from a machine outside the body.

• Internal: A thin needle or probe is inserted directly into the tumor. The tip of the probe releases energy, which heats the tissue around it.

Radiofrequency ablation

Radiofrequency ablation (RFA) is probably the most commonly used type of local hyperthermia. It uses high-energy radio waves for treatment. A thin, needle-like probe is placed into the tumor for a short time, usually about 10 to 15 minutes. Placement of the probe is guided by ultrasound or CT scans. The probe releases a high-frequency current that creates heat (between 122° and 212 °F) and destroys the cancer cells within a certain area.

RFA may be repeated for tumor recurrence, regrowth, or incomplete treatments. It can also be added to any other treatment, like surgery, radiation therapy, chemotherapy, hepatic arterial infusion therapy, alcohol ablation, or chemoembolization. RFA is most commonly used to treat tumors in the liver, and is being studied for use in several other areas of the body. Long-term RFA treatment outcomes are not yet known.

Regional hyperthermia

Regional hyperthermia heats a part of the body, such as an organ, limb, or body cavity (a hollow space within the body). It is usually combined with chemotherapy or radiation therapy. In one approach, called regional perfusion, the blood supply to a part of the body is isolated from the rest of the circulation. The blood in that part of the body is pumped into a heating device and then pumped back into the area (perfused) to heat it. This technique is being studied as treatment for certain cancers in the arms or legs, such as sarcomas and melanomas.

A related technique is being tested along with surgery against cancers in the peritoneum (the space in the body that contains the intestines and other digestive organs). During surgery, heated chemotherapy drugs are circulated through the peritoneal cavity. This is called continuous hyperthermic peritoneal perfusion, or CHPP.

Another approach to regional hyperthermia is deep tissue hyperthermia. This treatment uses devices that are placed on the surface of the organ or body cavity and produce high energy waves directed at a specific area. These devices give off radiofrequency or microwave energy to heat the area being treated.

Whole-body hyperthermia

Whole-body heating is being studied as a way to make chemotherapy more effective in treating cancer that has spread (metastatic cancer). Body temperature is raised by using warm-water blankets, inductive coils (like those in electric blankets), or thermal chambers (much like large incubators).

Pros and cons of hyperthermia

A major advantage of regional and whole body hyperthermia is that they seem to make other forms of cancer treatment work better. Heating cancer cells to temperatures above normal (up to as high as 113° F) makes them easier to destroy using radiation and certain chemotherapy drugs. And local hyperthermia, such as RFA, can use very high temperatures to destroy tumors without surgery.

Scientists agree that hyperthermia works best when the area being treated is kept within an exact temperature range for a certain period of time. But this isn't always easy to do. Keeping an area at a constant temperature without affecting nearby tissues can be tricky, too. To add to this, not all body tissues respond the same way to heat -- some are more sensitive than others. Another problem is monitoring the temperature at a specific site within the body. Small thermometers on the ends of probes are often placed in the treatment areas to be sure the temperature stays within the desired range.

Side effects

The possible side effects of hyperthermia depend on the technique being used and the part of the body being treated. Most side effects are short-term, but some can be serious. Localized or regional hyperthermia can cause pain at the site, infection, bleeding, blood clots, swelling, burns, blistering, and damage to the skin, muscles, and nerves near the treated area. Whole-body hyperthermia can cause nausea, vomiting, and diarrhea. More serious, though rare, side effects can include problems with the heart and blood vessels and other major organs. Experience, improved technology, and better skills in using hyperthermia treatment have led to fewer complications, and the problems that people do have are less serious.

The future of hyperthermia

While hyperthermia is a promising way to improve cancer treatment, it is largely an experimental technique at this time and is not commonly used. Many clinical trials of hyperthermia are now being done to better understand and improve this technique, and also look at how it is best used along with other cancer treatments. Current studies are looking at its usefulness in treating many types of cancer, including the following:

• breast
• cervical
• colorectal (with spread to liver)
• endometrial
• kidney
• liver
• lung
• ovarian
• pancreas
• prostate
• sarcomas (soft tissue cancers)
• thyroid

For more information about clinical trials of hyperthermia, contact the National Cancer Institute (NCI) at 1-800-4-CANCER or visit the NCI Web site at www.cancer.gov/clinicaltrials.

Additional resources*

National Cancer Institute
Toll-free number: 1-800-4-CANCER (1-800-422-6237)
Web site: www.cancer.gov

*Inclusion on this list does not imply endorsement by the American Cancer Society.

No matter who you are, we can help. Contact us anytime, day or night, for cancer-related information and support. Call us at 1-800-ACS-2345 or visit www.cancer.org.

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Revised: 04/07/2008