Hyperthermia Therapy

Hyperthermia Therapy

Also called: Local Hyperthermia, Microwave Therapy, Heat Therapy, Whole Body Hyperthermia, Regional Hyperthermia, Microwave Thermotherapy

Reviewed By:
Carol Kornmehl, MD, F.A.C.R.O
Martin E. Liebling, M.D., FACP

Summary

Hyperthermia therapy is the use of heat to damage or kill cancer cells. It is used to increase the effectiveness of other cancer treatments, such as chemotherapy or radiation therapy. In some situations, hyperthermia may used by itself to kill cancer cells directly.

Hyperthermia can be delivered via several methods. For the therapy to be effective, the proper amount of heat must be applied to a specific area over a given period of time. Hyperthermia uses heat between 106 degrees Fahrenheit and 113 degrees Fahrenheit (41 to 45 degrees Celsius) to alter the cancer cells while preventing the surrounding cells from becoming damaged.

At present, hyperthermia therapy is considered to be an experimental procedure and is not widely available. Only about 30 centers in the United States offer this treatment, according to the  American Cancer Society. However, there are many clinical trials under way exploring the use of hyperthermia therapy to treat several types of cancer.

About hyperthermia

Hyperthermia therapy is treatment that uses heat to change or kill cancer cells. Cells are altered when they encounter higher than normal temperatures, making them more susceptible to radiation therapy, chemotherapy and cancer vaccines. Extremely high temperatures are used to kill cancer cells directly.

Physicians first began to use heat to destroy tumors in the 19th century. For years, the potential cancer-fighting power of hyperthermia was limited by the difficulty in directing heat to the targeted cells without damaging other cells in the body. However, technological advances have made it easier to focus on cancer cells.

Scientists are unsure why hypertherapy improves the effectiveness of chemotherapy and radiation treatments. One theory is that higher temperatures improve blood flow to tumors. Better blood flow can deliver more chemotherapy drugs to cancer cells. It can also provide increased oxygen, which can make radiation therapy more effective.

Some researchers believe that high temperatures also may increase the strength of the immune system. Studies have shown that very high temperatures, such as seen with a fever, may help the immune system fight off infections. This increased strength may potentially fight off cancer cells and tumor growth.

Additional studies suggest that hyperthermia damages the nuclear structure of cells. The nucleus helps translate genetic information into proteins that allow the cells to function. The high temperatures may change or distroy cancer cells and prevent them from growing. Heat also alters the proteins that make up cells. This can render cancer cells more vulnerable to standard treatments.

Hyperthermia uses heat between 106 to 113 degrees Fahrenheit (41 to 45 degrees Celsius) to treat cancer by one of three main methods:

  • Local hyperthermia. Also known as thermal ablation, this involves using great heat – up to 113 degrees Fahrenheit (45 degrees Celsius) – to destroy a small area of cancer cells. A square or round box is placed outside the body over the tumor, and forms of energy – including radio waves, microwaves and ultrasound waves – are used to raise the temperature of the target area. The most commonly used technique is radiofrequency ablation (RFA), which uses high-energy radio waves to create the heat.

  • Regional hyperthermia. Involves raising the temperature of the body or part of the body to a level that is higher than normal through several methods. The heat disrupts the proteins and structures within the cells. This change may allow cancer treatments, such as radiation therapy, chemotherapy or other anticancer drugs, to work more effectively. Regional therapy is used to treat cancer in organs (such as the liver or lung), limbs or body cavities.

  • Whole-body hyperthermia. Patient receives the heat from warm-water blankets, inductive coils or thermal chambers (similar to large incubators). This type of hyperthermia increases the effectiveness of chemotherapy in treating cancers that are spreading (metastatic).

At this time, hyperthermia remains largely an experimental procedure. Only about 30 centers in the United States offer the therapy, according to the American Cancer Society. However, it is being studied in clinical trials to treat some cancers including:

  • Breast
  • Women’s reproductive cancers (e.g., endometrial)
  • Kidney
  • Liver
  • Lung
  • Pancreatic
  • Prostate
  • Soft tissues (sarcomas)
  • Thyroid

In many cases, clinical trials combining hyperthermia and other cancer treatments have resulted in a significant shrinkage in tumor size. Hyperthermia appears to be particularly effective when combined with radiation therapy. This combination is adept at damaging two types of cells resistant to radiation therapy alone:

  • Cells in the process of making DNA for replication.

  • Cells that are acidic and poorly oxygenated. Tumors frequently contain cells that are starved for oxygen, and these cells are particularly susceptible to hyperthermia. The treatment allows the cancer cells to be heated to higher temperatures than nearby healthy cells. Heat also prevents cells from repairing damage caused by radiation, which helps ensure that the initial destructive effect of radiation treatments have longer-lasting effect.

Before, during and after hyperthermia

Patients should follow all of the  preparatory steps recommended by their physician. These may include changes in medication regimens or dietary restrictions for a period prior to the procedure. Preparation for hyperthermia treatment depends on the type of procedure being used.

In order for hyperthermia to be successful, the proper amount of heat must be applied to a specific area over a given period of time. Small needles or tubes with tiny thermometers are inserted into the treatment area to monitor the temperature. Hyperthermia can be delivered via several methods, including:

  • Local hyperthermia. A small area of the body containing cancer cells is targeted. The energy used in this therapy comes from microwave, radiofrequency or ultrasound. It can be delivered with one of several methods, depending on the location of the tumor:

    • External. Used when the tumor is located on or near the body surface. A square or round box is placed outside the body over the tumor and a machine outside the body delivers high-energy waves to raise the temperature of the tumor tissues.
  • Internal or interstitial. Used on tumors that are deeper in the body. Ultrasound or a computed axial tomography (CAT) scan is used to guide a thin needle or probe through the cavity and to the site of the tumor. The probe is then inserted directly into the tumor. The tip of the probe releases energy that heats up the surrounding tissue. A version known as radiofrequency ablation (RFA) uses radio waves to heat and kill cancer cells. Internal local hyperthermia can raise the tissue temperature much higher than external local hyperthermia.

  • Intraluminal or endocavitary. Used to treat tumors found within or near body cavities. Examples include cancer of the esophagus or rectum. Probes are inserted into the cavity and directly into the tumor and energy is delivered to heat the area.
  • Regional hyperthermia. Used to treat larger areas, such as an organ, limb or body cavity. It can be administered in several ways. Such as:

    • Deep tissue. Used to treat cancers within the body, such as cervical cancer or bladder cancer. Applicators are placed externally on the body around the body cavity or organ to be treated, and microwave or radiofrequency energy is transmitted to the area to raise its temperature.

    • Regional perfusion. Separates the blood supply to a part of the body from the rest of the bloodstream. The isolated blood is pumped into a heating device and warmed before being returned to the area to be treated. This therapy is most often used to treat tumors that can be isolated from the circulatory system. Cancers in the arms or legs, such as sarcomas and melanomas, may benefit from this technique. Cancer in some organs, such as the liver or lung, may also benefit from this treatment. Anticancer drugs are frequently combined with this method of treatment. After the procedure the patient is hospitalized for three days with the treated extremity elevated.

    • Continuous hyperthermic peritoneal perfusion (CHPP). Used to treat cancers in the peritoneum (the body cavity containing the intestines and other digestive organs). It involves heating chemotherapy drugs and circulating them through the peritoneal cavity. During this procedure, the cavity temperature reaches 106 degrees Fahrenheit to 108 degrees Fahrenheit (41 to 42 degrees Celsius).

  • Whole-body heating. A newer approach known as whole-body heating is being explored as a means of increasing the effectiveness of chemotherapy in treating cancers that are spreading (metastatic). The patient receives the heat from warm-water blankets, inductive coils or thermal chambers (similar to large incubators). This technique can raise body temperatures to 107 or 108 degrees Fahrenheit (around 42 degrees Celsius).

A typical regimen might include application of heat twice a week for 60 minutes each session. Other treatments, such as whole-body heating, may require a treatment period of several hours. Hyperthermia sessions are usually scheduled a few days apart because cells are often resistant to the destructive effects of heat for several days after an exposure.

Hyperthermia is often used in combination with other cancer treatments. Radiation therapy or chemotherapy may be scheduled within an hour of a hyperthermia session, or may be administered simultaneously.

The Food and Drug Administration considers the combination of whole-body thermal therapy and chemotherapy an investigational procedure. For this reason, treatment must follow the research protocol for a specific clinical trial. Currently, there are several clinical trials approved by the National Cancer Institute that study hyperthermia and chemotherapy to treat various cancers.

Potential benefits and risks of hyperthermia

The biggest advantage of hyperthermia is its ability to increase the effectiveness of cancer treatments such as chemotherapy and radiation therapy. However, it can be very difficult to sustain the precise temperature over the period of time necessary to make hyperthermia effective. Other obstacles include:

  • Danger of overheating nearby healthy cells, which can occur at temperatures exceeding 111 degrees Fahrenheit (44 degrees Celsius)

  • Determining the right temperature to affect the cells, which varies from tissue to tissue

  • Difficulties in monitoring tissue temperatures

Most side effects associated with hyperthermia are temporary, but some can be serious. Because of the high temperatures involved, there is a risk of burns, blisters, discomfort or pain in the treated area. Other side effects may include:

  • Localized or regional therapy
    • Pain at the site
    • Bleeding
    • Blood clots
    • Swelling
    • Damage to nearby tissues

  • Whole-body therapy

    • Nausea
    • Vomiting
    • Dehydration
    • Diarrhea
    • Heart problems

Ongoing research regarding hyperthermia

Clinical trials continue to look at new ways that hyperthermia may be used to treat cancer. Studies are investigating the amount of heat therapy necessary to most effectively boost the role of radiation therapy in fighting cancer. Researchers are also working on techniques that use tissue samples to predict how a tumor will respond to hyperthermia treatment.

Researchers are pursuing several other potential improvements to using hyperthermia, including:

  • Manipulating the flow of blood to the tumor or the tumor’s sensitivity to heat

  • Computer-based treatment planning

  • Continuous heating over time in contrast to the standard, shorter technique

  • Determining ways to change the cell’s structure for improved response

  • Developing new methods to measure temperature and to keep it constant

Cancer specialists indicate that hyperthermia needs to undergo a considerable amount of research before it becomes a standard cancer therapy. However, clinical trials have shown promise to prevent the spread and recurrence of some cancers.

Questions for your doctor about hyperthermia

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about hyperthermia therapy:

  1. Is hyperthermia used to treat my form of cancer?
  2. Which type of hyperthermia might be used?
  3. Will it be combined with other forms of treatment?
  4. How would the treatment be administered and by whom?
  5. How often and for how long would I receive treatment?
  6. Would I receive the treatment as part of a clinical trial?
  7. Is there a local treatment center where this therapy is available?
  8. What are the risks associated with this treatment?
  9. What restrictions will I have with this treatment?
  10. What is the success with hyperthermia treatment for my form of cancer?
  11. How will my cancer be monitored during treatment?
  12. How will I know if the treatment has been successful?
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