Research in hyperthermia treatments
Hyperthermia treatment uses heat to destroy cancer cells and shrink tumours. Heat can harm or kill cancer cells by damaging proteins and structures within the cells. Heat also damages blood vessels inside of tumours and causes less blood flow to the tumour, which can help slow its growth. The temperature of the heat used in hyperthermia treatment is carefully controlled to limit damage to normal cells and tissues. Researchers have also found that heat can trigger an immune response that may help fight cancer.
Hyperthermia treatment is also called thermal therapy or thermotherapy.
Hyperthermia is under study in clinical trials (research studies with people) and is not widely available. Hyperthermia is sometimes given with other types of cancer treatment such as radiation therapy or chemotherapy, including embolization techniques that block off a blood vessel to directly deliver these treatments to specific areas of the body.
The damage to cells during hyperthermia can make them more sensitive to the effects of chemotherapy and radiation therapy so these treatments work better.
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
- how the cells and tissues react to the treatment and the location of the tumour
- your overall health and if you have other health problems (such as heart, liver or kidney diseases)
Hyperthermia treatments may be given to:
- a small area of the body (local hyperthermia)
- a large area of the body (regional hyperthermia)
- the whole body
Local hyperthermia uses very high temperatures to treat a small area like a tumour. Local hyperthermia is also called thermal ablation. It uses applicators that are placed near the tumour or within the tumour and energy is passed through them to heat the tumour.
This treatment can be given outside of the body (externally) to treat tumours in or just below the skin or it can be given to tumours inside of the body (internally).
Local hyperthermia may be used instead of surgery to treat cancer. It works best when the area being treated can be kept within a precise temperature range for the length of the treatment.
The following are different types of local hyperthermia treatments.
Radiofrequency ablation (RFA) uses high-frequency electrical waves 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 very high heat between 50°C and 100°C. The treatment lasts about 1 to 2 hours. The area may be numbed with local anesthetic (freezing), moderate sedation to make you sleepy (but you are conscious) or you may be given a general anesthetic to make you unconscious during RFA. RFA isn’t repeated unless more treatment is needed.
RFA may be used to treat tumours that can’t be removed with surgery, in people who aren’t able to have surgery and in cases where surgery is thought to be more risky than RFA. After RFA treatment is complete, the doctor uses imaging tests such as a CT or MRI scan to see if the tumours have shrunk or if they need more treatments.
RFA is used to treat tumours 5 cm and smaller in the liver, kidney and lungs. Researchers are studying RFA for the treatment of several other types of cancer.
Find out more about radiofrequency ablation.
Microwave ablation is a type of local internal hyperthermia treatment similar to RFA. But it uses a much higher frequency range than RFA, so more heat is given off and it can treat a larger area of tissue. 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, kidney, pancreatic and breast 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 prostate cancer that has not spread outside the prostate. They are also testing it in other types of cancer.
Regional hyperthermia uses low heat to treat cancer. The temperatures used in regional hyperthermia are usually between 40°C and 45°C. Regional hyperthermia may be used to heat large areas of tissue, such as an organ, body cavity or limb.
The following are different types of regional hyperthermia.
Some of the person’s blood is removed and heated. The heated blood is pumped back into the area that contains cancer. Chemotherapy may be pumped into the body at the same time. Regional perfusion is being studied as a way to treat some cancers in the arms or legs such as melanoma or soft tissue sarcoma. It may also be used to treat cancer in the liver or lung.
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 is being studied as a way to treat cervical or bladder cancer.
Whole-body hyperthermia uses low heat to raise a person’s body temperature to about 42°C. There are several ways that body temperature can be raised, such as using hot-water blankets, warm-water baths, heating coils or thermal chambers that are like large incubators. Researchers are studying whole-body hyperthermia in people whose cancer has spread (metastatic cancer).
Side effects of hyperthermia treatment
Side effects of hyperthermia treatment depend on the type of treatment given. The most common side effects of local hyperthermia include pain, infection, bleeding, swelling, burns and blisters. Regional hyperthermia can cause blood clots, bleeding, skin, muscle or nerve damage. The most common side effects of whole-body hyperthermia include nausea, vomiting and diarrhea.
Challenges with hyperthermia treatments
The main challenge of hyperthermia treatment is trying to make it work as well other types of cancer treatments. So far, the results are promising. Some types of hyperthermia are used to treat certain types of cancer as a first-line treatment. For example, tumours in the liver and lung may be treated with radiofrequency ablation. But more research and long-term studies are needed to find out if hyperthermia is as effective as surgery or radiation therapy for other types of cancer.
There are also other challenges to using hyperthermia that need to be figured out before some types of hyperthermia become a standard cancer treatment. With current methods it is sometimes hard to keep the body within an exact temperature range. 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.
I’m extremely grateful to the Canadian Cancer Society for funding my research with an Innovation Grant.
Great progress has been made
Some cancers, such as thyroid and testicular, have survival rates of over 90%. Other cancers, such as pancreatic, brain and esophageal, continue to have very low survival rates.