Hyperthermia as a palliative treatment measure for cancer
A state of hyperthermia as a potentially non-invasive treatment of malignant tumours in the body has been under intense research for some time now. The objective of hyperthermia treatment (also known as thermal therapy or thermotherapy) is to increase the temperature of a tumour in the body and in so doing, stimulate blood flow. This in turn increases oxygenation and sensitivity of the tumour cells, making them better targets for radiation therapy.
Hyperthermia treatment is thus being tested by radiation oncologists and research teams (so this technique is not yet widely available) as an additional method to be used alongside radiation therapy, giving specialists more control over malignant tumours, but without increased damage to healthier tissues, and other side-effects. In so doing, research teams and medical professionals are carefully assessing whether or not the practice can indeed adequately address the limitations of radiation therapy on its own, and increase potential for better outcomes. Radiation doses can be increased, but with fewer side-effects.
For those with various forms of cancer, who experience a recurrence of the disease, a second course of radiation is often not a good option for treatment due to the higher risk of healthy tissue damage. A second dose used in combination with hyperthermia treatment can potentially have a better effect on the cancerous cells of tumours with a reduced risk of side-effects and complications that can occur with just radiation therapy alone. In this way, re-treatment is being carefully looked at as a potentially more effective method for those with recurrent forms of cancer.
How does it work?
Body tissues are exposed to temperatures between 40°C and 45°C (104°F and 113°F). Targeted tissues are tumours located within a few centimetres of the surface of the skin. Those located deeper in the body, such as in the head, neck, breast or prostate are sometimes then reached via a probe. This carefully controlled heat damages the structure of cancer cells, killing them off (through a process known as thermal ablation). This allows for better shrinkage when combined with other treatment options such as radiation therapy or sometimes, chemotherapy too. Damaged cancer cells essentially become scar tissue and are allowed to shrink on their own for a period of time.
Increased heat in the body merely makes malignant cells more sensitive to radiation or chemotherapy, allowing the more traditional treatment to ‘do its job’ a little better with minimal harm to other portions of the body. Dual treatments will usually be scheduled on the same day (within an hour or so of one another).
Treatment methods for applying carefully medically controlled heat (2) include:
- Local hyperthermia: Heat is administered to a small area (tumour) using microwave, radiofrequency or ultrasound wave techniques. How heat is applied largely depends on where the tumour is located. Approaches can include external application (heat is externally applied to tumours that are within centimetres of the skin’s surface), intraluminal or endocavitary application (tumours are located in or near body cavities such as the rectum or oesophagus and can be easily reached with a probe which releases controlled heat energy) or interstitial application (probes or needles used in these techniques can reach deeper set tumours such as those in the brain, with the guidance of an ultrasound, and usually administered under anaesthetic).
- Regional hyperthermia: Heat is administered to larger areas such as limbs, organs or the body cavity. Ways this can be done include deep tissue methods (external applicators are positioned to administers microwave or radiofrequency heat energy), regional perfusion methods (blood is removed, heated and perfused / pumped back into the affected area such as the arm or leg, liver or lungs) or CHPP / continuous hyperthermic peritoneal perfusion methods (heated anticancer medications are administered to the peritoneal cavity, the space in the abdomen that contains the stomach, intestines and liver, via a warming device with the intention of reaching and treating cancerous cells of these internal organs).
- Whole-body hyperthermia: Cancer that is more widespread (metastatic cancer) in the body can be treated using a thermal chamber (much like a large incubator) and special hot water blankets. This technique may require the patient to be sedated with light anaesthesia to keep the person in a calm state during the treatment. The technique is also sometimes referred to as ‘fever-range whole-body hyperthermia’ because internal core body temperatures are raised to a fever level for a short period of time. His helps to give the immune system an extra boost to ‘fight’ cancer cells.
During the course of carefully applying heat to the body, medical professionals carefully control temperature so as not to exceed 45°C (113°F). Specialists will also carefully monitor the effects on surrounding tissue during the heating process. Local anaesthetic will be used when inserting probes or needles (tubes with small thermometers attached) to keep a close eye on the exact temperature of heat being applied. In order to reach precise locations, imaging techniques such as ultrasounds, MRI (magnetic resonance imaging) or CT (computerised tomography) scans will be used.
What could go wrong with hyperthermia treatment?
Heating the body above its normal core temperature is not without risk. Researchers stress that heat can be administered to around 43 / 44°C (111°F) before increased risk to other healthy tissues is likely to become affected. The higher the temperature, the more likely various regional spots in areas surrounding targeted tissues will be affected as well (in some cases damage can be irreversible). Most of the time, damage may be temporary, however, and can be effectively treated should it occur.
Maintaining an exact range of temperature for a very specific period of time without affecting other tissue areas can be tricky. Not all body tissues respond in the same way to heat, with some (such as the brain) being more sensitive than others.
With high heat applied locally comes the risk of discomfort, pain, infection and potential blisters or burns to the skin, nerves or muscles in the area being treated. Methods using perfusion applications can also increase the risk of bleeding, tissue swelling and blood clots. If whole-body heating is administered, there is an increased risk of vascular disorders or cardiac conditions (complications involving the blood vessels, heart or other vital organs). Mostly a person is at risk of experiencing manageable discomforts such as nausea and vomiting and / or diarrhoea.
Is hyperthermia set to become a viable treatment option for cancer?
Studies thus far have focussed on using this treatment combination on cancers of the brain, head and neck, oesophagus, thyroid, lung, breast, liver, kidney, appendix, pancreas, prostate, bladder, rectum, cervix, ovaries, endometrial lining (uterus) and peritoneal lining in the abdominal cavity. Other cancers treatment studies have focussed on include leukaemia, melanoma, sarcoma and neuroblastoma.
It is not yet a standard treatment practice and is still in the process of clinical trials. Long-term outcomes of using this method are also not yet known, making use as a standard practice a little way off.
Studies are ongoing and also include potential effects on patients also using certain anti-cancer medications. Some studies have not shown significant tumour size reduction following dual treatment or proven an increased rate of survival success. Clinical trials are also focussed on specific criteria, with many researching combination therapy effects, and others working to improve techniques used in applying heat for hyperthermia treatment.
For now, many agree that the future of these treatment methods appears promising, allowing for specialists and their teams to acquire new skills which may prove beneficial down the line for many cancer patients undergoing treatment.
2. National Cancer Institute. August 2011. Hyperthermia in Cancer Treatment: https://www.cancer.gov/about-cancer/treatment/types/surgery/hyperthermia-fact-sheet [Accessed 21.08.2017]