Inhibition of cell growth by irradiation in combination with hyperthermia or anticancer drugs.

Using a clonogenic assay and the human bladder cancer cell line T24, enhanced cytotoxicity by the combined use of irradiation and 43 degrees C hyperthermia or two anticancer drugs, bleomycin (BLM) and cis-dichlorodiammineplatinum (CDDP), has been investigated in vitro, as well as the size of colonies derived from single survivor cells after treatment. Irradiation combined with 43 degrees C hyperthermia showed greatly enhanced cytotoxicity and diminution in mean colony diameter and decreased distribution of colony size. BLM had almost the same effect as 43 degrees C hyperthermia in terms of cytotoxicity and colony size. While CDDP showed a certain degree of enhanced cytotoxicity in combination with irradiation, it produced no appreciable decrease in mean colony diameter. Hyperthermia may be beneficial in the management of radiation resistant cells surviving a large dose of radiation, and would seem to be a promising means for achieving eradication of cancer cells in combination with radiation therapy.