Dr. Sennewald Medizintechnik GmbH

Why hyperthermia increases the efficacy of radiation therapy by up to a factor of five

Hyperthermia and radiation therapy complement one another.

The thermal stimulus associated with hyperthermia treatment causes improved blood circulation and therefore improved oxygen supply to the tumor. This is important for increasing the efficacy of radiation therapy. Ionizing radiation destroys cancerous tissue primarily through the generation of oxygen radicals that attack the DNA of the cancer cells. Tumor cells containing insufficient oxygen are three times more resistant to ionizing radiation than normal cells. Thus, there is a direct relationship between hypoxia in human tumors and radiation therapy failure. Conversely, the higher the oxygen content in the cancerous tissue, the more effective the radiation therapy.

In addition to the creation of oxygen radicals that attack cancer cell DNA, hyperthermia also causes the accumulation of proteins in the cell nucleus. This prevents the self-repair of cancer cell DNA that is damaged by the ionizing radiation. In addition, ionizing radiation and damage cells during different phases of the cell cycle. Tumor cells are resistant to ionizing radiation during the synthesis phase, but they are susceptible to the destructive effects of hyperthermia during this phase.

Poorly perfused tumor tissue that is resistant to ionizing radiation is susceptible to hyperthermia.

In contrast, tumor tissue with good blood circulation does not react to the heat, but is susceptible to ionizing radiation. This complementary interaction is a compelling reason for combining hyperthermia and radiation therapy (thermoradiotherapy). In-vivo studies have shown that the use of hyperthermia can increase the effects of radiation therapy by a factor of between 1.2 and 5. This means that hyperthermia is one of the most effective potentiators of radiation therapy.

Synergistic mode of action of radiotherapy and hyperthermia