Hyperthermia as a complement to radiation therapy

The proven effect of hyperthermia in combination with radiation therapy is due to different mechanisms. Hyperthermia enhances radiation therapy. This has been substantiated by numerous comparative studies. In vivo studies have shown that hyperthermia can enhance the effect of radiation therapy by a factor of 1.2 to 5.

(1) Hypoxia
Radiation therapy is the more effective the higher the oxygen content is in the target area. The free oxygen radicals produced by the radiation damage the DNA. This effect has been corroborated in many trials. A moderate hyperthermia performed in close proximity in time to the radiation therapy is ideal for increasing the oxygen enrichment at the tumour location by promoting blood flow.

(2) Inhibition of DNA repair mechanisms
Each living cell has its own mechanisms for repairing ruptures in the DNA’s double helix. If however after the damage described a cell is subjected to additional stress, then these repair mechanisms are significantly disrupted. Heat is a possible stress factor of this sort. It can be used to enhance the desired effect of radiation therapy in the target area (“fix the damage”).

(3) Complementary sensitivities
Cells in a hypoxic state and in the lower PH scale as well as cells in the S-phase are less responsive to radiation therapy – yet they are more responsive to the aforementioned effects of hyperthermia. This means that the effects are complementary.

In summary, hyperthermia is probably the most potent radio sensitizer known at the present time.

(e.g.: N.R. Datta, S. Gómez Ordóñez, U.S. Gaipl b, M.M. Paulides c, H. Crezee, J. Gellermann, D. Marder, E. Puric, S. Bodis; May 2015)