Hyperthermia alone inhibits growth of the human esophageal cancer cell line (KSE-1). Even temporary exposure to hyperthermia results in substantial decreases in growth in a time- and temperature-dependent manner. A precipitous decrease in growth occurred at a temperature of approximately 42.5 °C. Concomitant application of hyperthermia, bleomycin and irradiation (hyperthermochemoradiotherapy, HCR) had a maximal effect on cell growth, compared to findings in cells treated with only one or two of these modalities. Fractionated hyperthermia (42 °C, 60 min) at a time interval of under 12 h was less effective than a single application (42 0 C, 120 min). However, over a 12-hour time interval, the effects of both treatments were similar. Fractionated HCR (hyperthermia: 42 °C, 60 min, chemotherapy: 2 ug/ml of bleomycin, 60 min, radiotherapy: 2 Gy) at a time interval of under 21 h was less effective than a single HCR (hyperthermia: 42 °C, 120 min, chemotherapy: 2 ug/ml of bleomycin, 120 min, radiotherapy: 4 Gy). We conclude that care should be taken regarding development of thermotolerance when combined modality therapy is given.
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