For over a hundred years, doctors have been trying to treat cancer patients by overheating tumor tissue. The technical term for this is hyperthermia. This heat application is intended to destroy cancer cells and make the tumor more sensitive, for example, to chemotherapy or radiotherapy. But many questions are still open. Despite years of scientific work, overheating is still not a standard cancer treatment procedure. And: The term hyperthermia includes a whole series of very different procedures - ranging from clinical trials at large cancer centers to more or less reputable applications in the context of "alternative medicine".
Previously, doctors experimented with cancer therapy with artificially produced fever. They used chemicals or natural "pyrogenic" substances, such as bacteria, which caused a sharp increase in body temperature. This proved too dangerous. However, the effects of fever on the immune system continue to be researched.
Today in cancer medicine, hyperthermia is all about targeted overheating of the body or of individual parts of the body from the outside.
Today, patients receive energy that heats the body or organs and tissues affected by a tumor. In order to increase the temperature, physicians primarily use electromagnetic waves: microwaves or radio waves, or even ultrasound. It is also possible to rinse the inside of the body with a heated liquid. An example is rinsing the abdominal cavity or bladder with heated chemo-solutions. Thermal beds or cushions are rarely used.
Depending on the method used, an artificial temperature increase to values between 40 and about 43 degrees Celsius is tested, rarely more. Experts also distinguish between whole-body hyperthermia and only local or regional hyperthermia: Local or regional means that the application of heat remains limited to the diseased organ or diseased body.
Not the goal of most hyperthermia procedures: to kill cancer cells directly by heat. The necessary even higher temperatures would also damage healthy tissue and even endanger those affected. What happens instead?
Due to the "heat stress", tumor cells are to become more sensitive: to natural processes of decomposition, but above all more sensitive to concomitant radiotherapy or chemotherapy.
Comparatively well documented are effects and possible side effects so far especially for the combination of overheating and chemotherapy. But that does not apply to all cancers: the best way to know about the benefits for sufferers with soft tissue sarcomas. After all, for a few other types of cancer there are first estimates of benefits by experts, for example in guidelines for doctors.
For most patients, however, there are still many questions about hyperthermia open - including possible side effects and strains.
One of the risks is that the spread of heat in the tissue can not yet be controlled well enough in many applications: that is, the question of whether it is "hot" enough in the tumor, but healthy tissue is not damaged. Hyperthermia is usually a burden on the cardiovascular system as well.
Although much research has been done, hyperthermia is not yet a standard procedure that could be used for every patient and for all types of cancer. Overheating, alone or in combination with chemotherapy or radiotherapy, should only be done in clinical trials, or at least under strictly controlled scientific conditions.
How can one evaluate whether hyperthermia makes sense for a patient? And: Which method of overheating is suitable in the specific case?
This depends mainly on two questions that should be addressed to the doctors:
- Is there good scientific literature on hyperthermia about my cancer?
- How do experts assess the benefits in my very own illness situation, for example in technical guidelines?
If there are any answers to these questions, there are other important points:
- Should hyperthermia be used concomitantly with chemotherapy or radiation or alone?
- Do the overheating increase the chances of recovery for me?
- Or can I only expect a delay of illness?
Those affected need to know that these questions can not currently be answered for most cancers. This is especially true when hyperthermia should not extend the standard treatment, is intended as a complementary procedure, but as the sole, alternative medical offer.
The possible side effects of overheating must also be taken into account in this consideration. Flat rate information is therefore difficult or impossible.
Local or surface hyperthermia
The affected area is "irradiated" from the outside with ultrasound, radio or microwaves. Local hyperthermia can be used on superficial, tight-subjacent tumors or superficial metastases. It can be used alone, but today it is usually combined with other therapies, such as chemotherapy or radiation.
The procedure is similar to an irradiation, but it takes longer: You lie on a couch under the hyperthermia device during the application.
An example of the application - but so far without a fixed status - is a local relapse in patients with breast cancer, especially with so-called chest wall relapses.
Surface hyperthermia is here combined with radiotherapy.
The idea behind it: Because the heat amplifies the effect of radiotherapy, low-dose radiation may even be used to irradiate women who previously had radiation from this body region and would not be able to tolerate a normal dose again.
However, this application is not standard.
Regional (deep) hyperthermia
Not only the actual tumor, but larger body regions are heated. This is also to lower tumors and metastases are achieved.
- In tumors of the rectum (rectal carcinoma), the pelvic area and lower abdomen are in the hyperthermia field.
- In the case of soft tissue sarcomas on the extremities, the entire affected leg or arm is treated.
In regional hyperthermia, physicians and medical physicists today mostly work with electromagnetic waves. Modern hyperthermia units consist of a so-called ring applicator, which generates electromagnetic waves. As a patient, one lies on a couch in a kind of ring, which carries the actual radiators. By means of suitable control they produce controllable heating - within limits. In order to guide the electromagnetic waves, one is also embedded in a kind of water cushion.
Overheating in normal tissue can be largely avoided, the high temperature is thus largely limited to the tumor.
Again, a standard procedure, these applications are not yet, even if the data for the benefit, especially for soft tissue sarcomas is comparatively good.
"Antennas" or probes are placed in the tumor or on its surface, allowing for heating directly inside the tumor. This procedure is also part of regional hyperthermia.
Depending on the situation, the probes can be brought to the tumor via natural orifices, for example via the esophagus or intestine.
If this is not possible, the patient will receive local anesthesia or light anesthesia before placing the probes. This form of hyperthermia is used in most patients in combination with brachytherapy, ie radiation also "from the inside".
This form of hyperthermia can be used in advanced and recurrent head and neck cancer, or in men with prostate cancer.
Again, it should be used only under study conditions, so the recommendation of the professional societies - a proven standard therapy is not hyperthermia.
Whole body hyperthermia
The entire body is heated. Doctors used to use hot water or liquid-filled upholstery or blankets and similar procedures. Today, overheating with electromagnetic waves or infrared is also an option.
The aim: This approach is being studied to treat cancers that have already spread throughout the body and metastasized.
What you should know: The benefits and side effects of whole-body hyperthermia are much more open than local or regional procedures. Therefore it should only be used under study conditions. In fact, it is currently being propagated mainly in alternative or complementary medicine.
Hyperthermia with magnetizable nanoparticles, "Nano-cancer therapy"
In this form of hyperthermia tiny particles of iron are used, so-called nanoparticles. These particles, depending on their chemical "packaging", can accumulate particularly well in tumor tissue. In some approaches, doctors also deliver magnetizable nanoparticles directly into the tumor.
An electromagnetic field can be used to control the heating of these particles. The future significance of this approach can not be estimated at present - so far mainly preclinical, highly experimental tests are available.
For example: Clinical studies have so far been performed predominantly in patients with brain tumors.
Hyperthermic perfusion and HIPEC
Rather than a modification of chemotherapy because hyperthermia in the true sense, two other methods.
In hyperthermic perfusion for regional hyperthermia, the patient is given a heated fluid, such as a chemotherapy solution: it is flushed through the afferent veins of the cancerous body part. This approach is usually associated with surgery, which also requires anesthesia. Perfusion, like many of these hyperthermia procedures, is not standard.
In hyperthermic intraperitoneal chemotherapy (HIPEC), the application is slightly different: Here, body cavities are flushed with hot chemotherapy solution.
The most important example is a hyperthermic perfusion, which is used when the peritoneum is attacked by tumor cells. After removal of the tumor located in the abdomen, for example, a stomach or pancreatic cancer or ovarian cancer, the chemotherapy solution is heated and used to flush the abdominal cavity.
Another example: Overheated bladder irrigation is also discussed by experts.
HIPEC is also a form of therapy that, according to experts, should only be used in studies.
In a broader sense, some other methods also work with the targeted overheating of tissue. This is more of a kind of "cooking" and not hyperthermia. For example, high-frequency-induced thermotherapy (HITT) and laser-induced thermotherapy (LITT) use extreme.
At HITT, the doctors push a needle electrode into the patient's tumor during a minor procedure. Usually a local anesthetic or a light anesthetic form is enough. In the tumor, the electrode generates temperatures between 56 and 100 degrees Celsius, where tissue is directly damaged.
At LITT, a fiber optic light guide is advanced into the tumor tissue. The tissue is then heated and destroyed by long wavelength laser light. As with the HITT, temperatures are in an area that directly destroys tissue.
Both procedures, HITT and LITT, are only suitable for a few tumor types and are not a real alternative to surgery. Most experience is in patients with liver metastases or liver cancer.
The HIFU bundles ultrasonic waves and uses them to heat tumor tissue. This "high-intensity focused ultrasound" (HIFU) is mostly used only for the treatment of prostate cancer and is also not a standard.
This can happen: Unwanted temperature increases in healthy tissue are still one of the most important problems, even if patients usually only have to reckon with redness or swelling of the skin in the treated region of the body, depending on the application.
True burns are rare, if not excluded, with good control. Also possible are temporary and sometimes prolonged pain in the overheated region. Hyperthermia is also a burden for the heart and circulation. Above all, whole-body hyperthermia is therefore often excluded for patients with pre-existing conditions.
On the other hand, experts call for patients to be monitored well during treatment - to control temperature in the target tissue, to quickly cool affected tissues as needed, or to provide rapid relief from pain with appropriate medications.
Sometimes it is also necessary to completely stop the therapy if the side effects are too severe. Whole body hyperthermia may even require intensive care monitoring.
If hyperthermia treatment is used with chemotherapy and / or radiation, patients should also be aware of the side effects of these treatments. Since hyperthermia is supposed to increase the effect of both methods, the side effects may become more pronounced.
What does the heat do in itself? Experiments have shown that temperatures of at least 42.5 to 43 degrees Celsius over a period of about 40 to 60 minutes are needed to kill cancer cells.
At lower temperatures, longer treatment times are needed to damage cells.
Hyperthermia is usually used today in addition to radiation and chemotherapy. In clinical studies, an intensifying effect of hyperthermia was observed. The underlying biological relationships are complex, but so far only partially elucidated.
In long-lasting and / or repeated Hyperthermiebehandlung form cells in temperature ranges of about 41 to 43 degrees Celsius so-called heat shock proteins (HSP), also called Stresseiweiße. These proteins are signals for the body's own killer cells of the immune system to break down "damaged" cells.