Anti-tumor effect of cisplatin, carboplatin, mitoxantrone, and doxorubicin on peritoneal tumor growth after intraperitoneal and intravenous chemotherapy: a comparative study.

Tumor growth was studied in a peritoneal tumor model in the rat after intravenous and intraperitoneal administration of doxorubicin (4 mg/kg), mitoxantrone (2.5 mg/kg) and cisplatin (4 mg/kg) and after intraperitoneal administration of carboplatin (20 mg/kg). All treatments delayed tumor growth and intraperitoneal treatment was more effective initially than intravenous treatment for all drugs tested. Regrowth occurred between 2 and 7 weeks after treatment and was less pronounced after intravenous treatment. Tumor sizes in cisplatin treated rats 7 weeks after treatment were comparable after intraperitoneal and intravenous treatments. Intraperitoneal carboplatin even with a dose 5 times higher than cisplatin resulted in a less tumor growth delay in all stages of the treatment, compared to cisplatin. All cytostatic drugs, except carboplatin, induced loss of body weight. Weight loss was similar for intraperitoneal and intravenous treatment with both cisplatin and mitoxantrone while for doxorubicin the weight loss was significantly higher after intravenous treatment than after intraperitoneal therapy. Considering the "therapeutic index", defined as the ratio of tumor growth delay to weight loss, cisplatin had the highest "therapeutic index", 1.5 (intraperitoneal) and 1.7 (intravenous) compared to 0.3 (intraperitoneal) and 0.6 (intravenous) for Mitoxantrone and 0.4 (intraperitoneal) and 0.5 (intravenous) for doxorubicin. This indicated that cisplatin was the most favorable drug to use in this peritoneal tumor model for both intraperitoneal and intravenous treatment. The tumor growth delay was initially more pronounced after intraperitoneal cisplatin compared with intravenous.