Intratumoral cisplatin administration in electrochemotherapy: antitumor effectiveness, sequence dependence and platinum content.

Electrochemotherapy using intratumoral cisplatin administration was tested on EAT tumors in mice. Mice were treated with eight electric pulses (100 micros, 1 Hz, 1040 V) and/or cisplatin (1, 2, 4 and 8 mg/kg). Cisplatin treatment resulted in up to 20 days of tumor growth delay. Electrochemotherapy resulted in tumor cures; local tumor control reached a plateau at 4 mg/kg in 67% of tumor cures. The maximal effect of electrochemotherapy was achieved when cisplatin was injected 5 min before or simultaneously with electric pulses application. Approximately two times more platinum was bound to DNA in electrochemotherapy than in cisplatin treated tumors at all time points tested. Our study shows that electrochemotherapy with intratumoral cisplatin administration is a very effective local treatment of EAT tumors with high curability rate.