The Effect of Rectangular Electric Pulse Number in Electrochemotherapy by Low Voltage and High Frequency on Breast Tumors in Balb/c Mice

Objective: The treatment efficiency of electrochemotherapy (ECT) or the use of a chemo- therapy agent with a high electric field and low frequency has been reported. Unfortunate- ly this protocol induces an unpleasant sensation to the patient. Therefore, the aim of this study was to investigate the efficiency of combined low electric field and high repetition frequency for the treatment of an animal tumor model, invasive ductal carcinoma. Materials and Methods: Female Balb/c mice were transplanted with invasive ductal car- cinoma. ECT with bleomycin and two different electric pulse simulation protocols were used. In the first protocol, eight high pulses at an amplitude of 1000 V/cm with 100 ?s duration and repetition frequencies of both 5 kHz and 1 Hz were delivered. In the second protocol, low pulse amplitude of 100 V/cm with 5 kHz frequency and different numbers of pulses 500 (1 pulse with 50 milliseconds duration), 2000 (4 pulses with 50 milliseconds duration), 4000 (8 pulses with 50 milliseconds duration) and 5000 (10 pulses with 50 mil- lisecond duration) at 100 ?s were applied. Results: ECT with a higher repetition frequency of electric pulses and low voltage inhib- its tumor growth and has a comparable effect to the 5 kHz and 1 Hz pulse repetitions at high voltage. Based on the results, the best antitumor effect was obtained at 4000 pulses or higher, with high frequency and low voltage (p < 0.05). The rate of inhibition of tumor growth statistically increased with electric pulse numbers higher than 2000. Conclusion: The finding indicated that ECT with the use of low pulse amplitude and high frequency, combined with the best number of pulses has a comparable effect to a clinical protocol.