Research in hyperthermia treatments
Hyperthermia treatment is also called thermal therapy or thermotherapy. It uses heat to destroy cancer cells and shrink tumours. The temperature is carefully controlled to limit damage to normal cells and tissues. Heat can harm and kill cancer cells by damaging proteins and structures within the cells. Heat also damages tumour blood vessels and causes less blood flow to the tumour. Researchers have recently found that hyperthermia can trigger an immune response that also helps to fight cancer.
Types of hyperthermia treatments
Researchers are studying many types of hyperthermia treatments. How well hyperthermia treatment works is related to the temperature that can be reached during treatment, the length of treatment and the characteristics of the cells and tissue treated. Researchers are studying hyperthermia in clinical trials to try to find out how it can be used to treat cancer.
Hyperthermia treatments may be given twice a week, once a week or once a month, depending on which other treatments are given. Most hyperthermia treatments last 60–90 minutes. Hyperthermia treatment can be given to a small area (locally), to a large area of tissue or the body (regionally) or to the whole body.
Local hyperthermia is also called thermal ablation. Very high heat is applied to a small area, usually the tumour itself.
Local hyperthermia can be given externally or internally. External local hyperthermia treats tumours in or just below the skin. External applicators are placed near the tumour and energy is passed through them to heat the tumour. Internal local hyperthermia uses special probes or needles placed inside a body cavity (intraluminal) or into a tumour (interstitial) deep within the body.
Local hyperthermia may be used instead of surgery to treat cancer. Local hyperthermia works best when the area being treated can be kept within a precise temperature range for a certain amount of time.
The following are different types of local hyperthermia treatments.
Radiofrequency ablation (RFA) uses a high-frequency electrical current to create heat to destroy cancer cells. A thin needle-like probe delivers the electrical current directly into the tumour. The doctor uses an ultrasound, an MRI or a CT scan to guide the probe to the tumour. The tip of the probe delivers heat between 50°C and 100°C. The treatment lasts about 10–30 minutes. The area may be numbed with local anesthetic (freezing) or you may be given a general anesthetic to make you unconscious during RFA.
RFA may be used to treat tumours that can’t be removed with surgery. It may also be used in people who are not good candidates for surgery. A person may need to have several treatment sessions. After RFA treatment is complete, the doctor uses a CT scan to see if the tumours have shrunk or if more treatment is needed. RFA can be used along with other cancer treatments.
RFA is best used to treat tumours 4 cm and smaller. It is most often used for tumours in the liver, kidney and lungs. Researchers are studying RFA for the treatment of several other types of cancer.
Microwave ablation is a type of local internal hyperthermia treatment similar to RFA. The doctor places one or more probes that deliver microwaves into the tumour. Most research is looking at microwave ablation for the treatment of liver, lung and kidney cancers.
High-intensity focused ultrasound
High-intensity focused ultrasound (HIFU) is a type of local external hyperthermia treatment. HIFU uses focused ultrasound waves to create intense heat, which destroys tissue. Often an MRI is used to guide the ultrasound beam. Researchers have mainly looked at this procedure as a primary treatment for men with localized prostate cancer. They are also testing it in other types of cancer.
Regional hyperthermia uses low heat to treat cancer. Regional hyperthermia may be used to heat large areas of tissue, such as an organ, body cavity or limb. It may be combined with chemotherapy or radiation therapy.
The following are different types of regional hyperthermia.
Some of the person’s blood is removed and heated to between 40°C and 45°C. The heated blood is pumped, or perfused, back into the area that contains cancer. Chemotherapy may be pumped into the body at the same time. Regional perfusion may be used to treat some cancers in the arms or legs such as melanoma or soft tissue sarcoma. It may also be used to treat liver and lung cancers.
Hyperthermic intraperitoneal chemotherapy
Hyperthermic intraperitoneal chemotherapy (HIPEC) is also called continuous hyperthermic peritoneal perfusion. It can be used with surgery to treat cancers in the abdominal (peritoneal) cavity such as peritoneal mesothelioma, stomach, colorectal and liver cancers. Heated chemotherapy drugs flow through a warming device and are then pumped into the peritoneal cavity.
Deep tissue regional hyperthermia
Microwave or radiofrequency energy is passed from a device placed on the surface of an organ or body cavity. The energy given off by the device makes heat, which can be used to treat an area that has cancer. Deep tissue regional hyperthermia may be used to treat cervical or bladder cancer.
Whole-body hyperthermia uses low heat to raise a person’s body temperature. There are several ways that body temperature can be raised, such as using hot-water blankets, warm-water baths, special coiled devices or special thermal chambers that are like large incubators. Researchers are studying whole-body hyperthermia in people whose cancer has spread (metastatic cancer).
Hyperthermia and cancer treatments
Hyperthermia treatment is usually given with other types of cancer treatment, such as chemotherapy or radiation therapy. It may make some cancer cells more sensitive to radiation or destroy cancer cells that are not killed by radiation therapy. Hyperthermia may also help other cancer treatments, such as chemotherapy or immunotherapy, work better.
Challenges with hyperthermia treatments
The main challenge of hyperthermia is to make sure the hyperthermia cancer treatment is as effective as surgery or radiation therapy. So far, the results are promising and hyperthermia may be as effective as surgery or radiation for treating certain tumours, but more research and long-term studies are needed.
There are also other challenges to using hyperthermia that need to be figured out before it becomes a standard cancer treatment. These challenges include keeping the body within an exact temperature range and being able to accurately monitor temperature inside of a tumour. Researchers are trying to find better ways to monitor temperature during hyperthermia treatment. Some studies are using thermometers on the end of a probe to measure temperature during treatment. An MRI may also be helpful in monitoring temperature.
Researchers are also trying to find out how to use hyperthermia to treat tumours inside deeper organs of the body.
A treatment that uses and strengthens the immune system to fight disease including cancer.
Immunotherapy is a type of biological therapy.
I’m extremely grateful to the Canadian Cancer Society for funding my research with an Innovation Grant.
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