Chemotherapy and hormonal therapy of mouse mammary tumors

Single Cisplatin (Platinol) injections i.p. at 10 mg/kg dose level (LD10) caused a marked growth inhibition of both hormone dependent and independent GR mouse mammary tumors (reduction in tumor volumes of 86 and 85%, respectively). However this treatment caused severe toxic side effects including loss of mouse body weight and deaths of some of the animals. When Cisplatin (pure) was administered s.c. in a single cholesterol pellet, no such toxic effects were observed even when Cisplatin levels up to 30 mg/kg were applied. The latter dose caused 29% reduction in tumor volume of hormone independent tumors. However this inhibitory effect was temporary, since regrowth of the hormone independent tumors started again 8 days after application of the single Cisplatin pellet. These results show that continuous Cisplatin administration in pellets s.c. is less toxic than injection i.p., but that the inhibition of mammary tumor growth is also less marked.