Effect of the combination of hyperthermia and irradiation on human colon cancer cells.

The combination of hyperthermia and radiation is considered to have a synergistic effect on mammalian cells, which depends on temperature and duration of time of the hyperthermia and on the sequence in which the modalities are given. The response of cultured colon cancer cells to hyperthermia and ionizing radiation was evaluated using the flow cytometry method by measuring DNA damage. The enhanced DNA damage after combined treatment with hyperthermia and irradiation was recognized after both sequences: heat followed by radiation as well as radiation followed by heat. The results demonstrated that the sequence of radiation plus heat produced more DNA damage on colon cancer cells than did the reverse order. The clinical application of these results is discussed.