Enhancement of the potentiation of radiotherapy by platinum drugs in a mouse tumor.

This study examines two ways to enhance cisplatin-mediated potentiation of the radiotherapy of a mouse mammary tumor, MTG-B: a) the appropriate sequencing of the two modalities, and b) the use of platinum "rescue" at appropriate times relative to injection of cisplatin to ameliorate platinum toxicity and permit the use of larger concentrations of cisplatin. Reduced TCD50 values and potentiated tumor regression resulted when cisplatin preceded irradiation by 1 hr compared to injection of cisplatin post-irradiation. Cisplatin "rescue" was demonstrated by DDTC, WR-2721 and 5-TG, and enhanced effects on the inhibition of tumor growth resulted when 20 mg/kg cisplatin and 730 mg/kg DDTC were combined with radiotherapy.