Treatment of hepatic metastases of colorectal cancer by electrochemotherapy:: An experimental study in the rat

Background. Electrochemotherapy, which consists of local or systemic administration of a cytotoxic agent followed by application of electric pulses to a tumor, has proved effective for various types of tumors in animals and for cutaneous and head and neck cancers in human beings. This is the first study to investigate the efficacy of electrochemotherapy for treatment of hepatic metastases of colorectal cancer in the rat. Methods. After induction of a solitary hepatic metastasis in 36 male BDIX rats, the animals were randomized to one of four groups: B-E- (no treatment), B+E- (intratumoral bleomycin), B-E+ (application of electric pulses to the tumor), and B+E+ (electrochemotherapy: intratumoral bleomycin followed by application of electric pulses). Results. Groups B-E- and B-E+ had no tumor response. Group B+E- had one partial response. Group B+E+ had seven partial responses and two complete responses. The difference in terms of response between group B+E+ and the other three groups was statistically significant (P <.05). comparison of the mean posttherapy tumor volumes (B-E-, 50.6 mm(3) B+E-, 58.7 mm(3); B-E+, 46 mm(3); and B+E+ 5.65 mm(3)) revealed a significantly smaller residual tumor in group B+E+ than in the other three groups (P < .05). Conclusions. Electrochemotherapy is an effective means to reduce the volume of hepatic metastases of colorectal cancer in the rat. Additional research is required to determine the optimum treatment duration, dose effects, volume of tumor that can be treated by electrochemotherapy, and impact on survival. Such experimental studies are indispensable prerequisites for clinical trials.