What Is Hyperthermia – Heat Treatment? Does It Have a Role in Cancer Treatment?

What is hyperthermia treatment?

Hyperthermia (heat treatment or thermotherapy) is a cancer treatment method exposing body tissue to high temperatures (between 39 – 44 °C). Research has shown that high temperatures damage or kill cancer cells while causing very little harm to normal tissues. Hyperthermia may shrink tumors by killing cancer cells and damaging proteins and cellular structure.

How is hyperthermia used in cancer treatment?

Hyperthermia is mostly used together with other cancer treatments such as radiotherapy and chemotherapy. It may make some cancer cells more sensitive to radiation or damage cancer cells that radiation cannot harm. When hyperthermia and radiotherapy are used together, it is applied approximately 1 – 2 hours before radiotherapy. Hyperthermia may also increase the effects of some cancer drugs (chemotherapies).

Numerous clinical studies have investigated treatments combining hyperthermia with radiotherapy and/or chemotherapy. They focused on many cancer types, including sarcoma, melanoma, head and neck, brain, lung, esophageal, breast, bladder, rectal, liver, appendix and cervical cancers and mesothelioma (cancers of the lung and abdominal linings). Many, though not all, found that hyperthermia significantly shrank tumors when given with other treatments.

Hyperthermia treatment methods

Hyperthermia methods can be classified under 3 headings: Local, regional and whole-body hyperthermia

Local hyperthermia treatment

It applies heat using various techniques delivering high amounts of energy to heat the tumor and a limited surrounding area. Ablation is the heading for these methods, which reach higher temperatures than conventional hyperthermia, burning tumor tissue; their application is therefore limited, and they are used in relatively smaller tumors.

To apply heat in local hyperthermia, different energy types such as microwaves, radiofrequency and ultrasound can be used. Different approaches exist depending on tumor location:

• External approaches treat tumors just beneath or within the skin. External applicators are placed beside or around the appropriate region and energy is focused on the tumor to increase temperature.
• To treat tumors near or within body cavities such as the esophagus or rectum, intraluminal or endocavitary methods can be used. A probe is placed into the cavity and inserted into the tumor to deliver energy and heat directly.
• To treat tumors deep within the body, such as in the liver and prostate, interstitial (within or between tissues) methods are used. They allow higher temperatures to reach the tumor than external methods. A probe or needle is inserted into the tumor under anesthesia. Imaging such as ultrasound can ensure correct placement. The heat source is then inserted into the probe. Radiofrequency ablationis an interstitial hyperthermia method using radio waves to deliver heat to and kill cancer cells.

Regional hyperthermia treatment

Various approaches deliver heat to broad tissue areas such as a body cavity, organ or limb.

To treat cancer types such as cervical or bladder cancer, deep tissue approaches may be used. External applicators are placed around the body cavity or on the organ for treatment, and microwave or radiofrequency energy is focused on this area to raise temperature.

Regional hyperthermia was developed after many years of cancer treatment research. Based on heating the tumor region with radiofrequency waves, it can safely and effectively increase the effectiveness of existing cancer treatments such as chemotherapy and radiotherapy.

In this method, also called “regional deep electrohyperthermia,” intense energy is applied to the tumor region, with a target tissue temperature between 42 °C – 44 °C. During treatments lasting 60-90 minutes, the patient lies comfortably on the treatment bed. Adjustable short energy waves pass through healthy tissues via an applicator / electrode and concentrate in the tumor area. This temperature damages cancer cells.

Tumor cells hide from the immune system using various cellular mechanisms. Under the effect of heat delivered through regional hyperthermia, however, these cells can become visible. In this way, hyperthermia may make radiotherapy and/or chemotherapy more effective. In some cases, previously ineffective chemotherapy and/or radiotherapy may become effective when used with hyperthermia.

Also, unlike conventional regional hyperthermia, to treat cancers in arms and legs such as melanoma or cancers in organs such as the liver or lungs, regional perfusion methods may be used. Blood is taken from some patients, heated and injected back into the limb or organ. Cancer drugs are generally given during this treatment.

To treat all cancers within the peritoneal cavity (the abdominal space containing bowel, liver and stomach), including primary peritoneal mesothelioma and stomach cancer, continuous hyperthermic peritoneal perfusion HIPEC is used. During surgery, heated cancer medication flows into the peritoneal cavity. Peritoneal cavity temperature reaches 38 - 40°C.

Whole-body hyperthermia treatment

To induce one of the oldest treatment principles, fever , lamps emitting deeply effective, water-filtered infrared-A radiation that does not damage the skin are directed at the abdomen and torso. During the procedure, vital functions (blood pressure, pulse, oxygen saturation, respiratory rate and body temperature) are closely monitored, ensuring a controlled, targeted rise in body temperature. Because studies show optimal temperatures for immune activation are 39 °C – 40 °C, the target in cancer treatment is 39 °C – 40 °C, also called “moderate” whole-body hyperthermia. Treatment varies with the body’s response and time to reach the target, but lasts approximately 4 hours on average.

In whole-body hyperthermia, lamps emitting deeply effective water-filtered infrared-A radiation that does not damage the skin are directed at the abdomen and torso to induce fever, one of the oldest treatment principles. Because studies show optimal temperatures for immune activation are 39 °C – 40 °C, the target in cancer treatment is 39 °C – 40 °C, also called “moderate” whole-body hyperthermia. Treatment varies with the body’s response and time to reach the target, but lasts approximately 4 hours on average.

The fundamental role of whole-body hyperthermia in cancer treatment is increasing the effectiveness of accompanying chemotherapy and strengthening the immune system. Particularly in patients with widespread tumors, it may increase treatment effectiveness when given with chemotherapy and also trigger a measurable increase in immune function.

Hyperthermia’s effect depends on cell and tissue characteristics, treatment duration and temperature reached during treatment. Temperatures in the tumor and surrounding tissue are monitored throughout to ensure the desired temperature is reached without exceeding it. In some applications, a small needle or tube with a mini thermometer may be placed in the treatment area under local anesthesia for temperature monitoring. Imaging such as computed tomography (CT) may be used to ensure correct probe placement.

Hyperthermia treatment side effects

Most normal tissues are not harmed during hyperthermia if temperature remains below 42-43°C. The most frequently used 3 hyperthermia methods (RFA = radiofrequency ablation, local hyperthermia and whole-body hyperthermia) generally cause no side effects because temperature increases are controlled or restricted to a very limited area. However, high-temperature effects may occur differently because of regional tissue differences. These may cause burns, blisters, discomfort or pain.

Conclusion:

Using specially developed devices, aiming to increase a patient’s whole-body temperature or the tumor temperature regionally, “Hyperthermia methods” have now become an important treatment option for many diseases. Numerous studies show that hyperthermia, meaning heat treatment, increases chemotherapy and radiotherapy effectiveness when used for cancer, a disease with many subtypes. In this form, hyperthermia is an evidence-based complementary method in cancer.