From the ancient times, attempts were made to treat cancer with “heat.” In the latter half of the twentieth century, cancer cells were found to be exterminated by heat (greater than 42°C), and benefits of this phenomenon in cancer treatment prompted the advancement of many research. As a result, various research results were published, including the cancer cells in acidic cancer tissues being susceptible to heat, the radiotherapy-resistant cancer cells in the latter half of S phase being susceptible to heat, and additive effect being obtained by the combination of heat and anticancer drug. These discoveries led to the proposal of hyperthermia treatment, which is a treatment of cancer using heat. Heating devices using radio waves, microwaves, and ultrasonic waves have been developed for this treatment, and certain results have been achieved, including the capability in treating relatively large tumor and high therapeutic effect in combination with radiotherapy and anticancer drugs. For details, please refer to the website of the Japanese Society for Thermal Medicine (FAQs on hyperthermia treatment).
The human body is a contrary being; when heat is applied from the outside, the body attempts to cool itself down. Even when a large amount of energy is applied to the body (e.g., 1,500 W in electric energy), a lot of this is excreted as waste materials, and the temperature is not raised as expected. It was found that both the patients and medical staff need to exert efforts in the treatment. The theory of “oncothermia” proposed by Professor A. Szasz has gathered attention under these circumstances. When electromagnetic waves are applied to the cancer tissues with modulated voltage focusing on impedance matching of radio waves, cancer tissues (cells) with histological heterogeneity cause the energy to gather at the surface, enabling the treatment of cancer at low electric energy (150 W).
The device for this oncothermia treatment was introduced to Toyama University Hospital. The device is characterized by an increase in temperature but with low power (150 W) due to the utilization of the effects of electromagnetic waves other than heat. For this reason, shield room is not required, and the treatment is relatively safe with extremely low likelihood of adverse drug reactions (such as burns) and the use of excessive heat that causes treatment to be discontinued. Oncothermia has been used mainly in the European countries; however, the utilization has extended to countries such as Korea, China, and Taiwan.
In compensation to the low risk of adverse reactions, it may be difficult to treat cancer with this treatment alone. However, a certain clinical efficacy has been observed when this treatment was used in combination with radiotherapy and anticancer drugs (clinical efficacy depends on factors such as the state of the disorder and circumstances of prior treatment). There are issues with cancer treatment using electromagnetic waves, such as the tracking of real-time body temperature; however, further development is expected in the future.
See Figure 1 and Figure 2.
OTM shows significant morphological changes in the cell (top), greater number of dead cells with green luminance (middle), and significant gene expression related to cell death (red-colored gene) (bottom). From the presentation by Dr. G. Andocs.
In oncothermia, the manner in which electromagnetic wave is radiated is designed so that cancer can be treated efficiently by minimal electric power use. This includes impedance matching, fractal modulation, and low-output heating.