Responses of RIF tumors to heat and drugs: dependence on tumor size.

The effects of hyperthermia and drugs on RIF tumors of three sizes were studied in C3H mice. The animals were treated with bleomycin, carmustine, or a combination of both drugs and with or without concomitant localized hyperthermia. The hyperthermia dose was 44 degrees C for 30 minutes for each treatment. Each animal was given two treatments, 7 days apart. The tumors were classified according to approximate size: 0.1, 0.3, or 0.7 cm3. Among the animals bearing the smaller tumors, no cures were observed. Growth delay measurements indicated that heat and drugs had approximately additive effects. Several cures were seen among the animals bearing medium- and large-sized tumors. Our results indicate that medium and large tumors may respond better to the combination treatment than small tumors.