Operating Procedures of the Electrochemotherapy for Treatment of Tumor in Dogs and Cats

The overall goal of this procedure is to treat cutaneous and subcutaneous tumors in dogs and cats with the use of cytostatic drugs in combination with the application of electric pulses. Electrochemotherapy is a local approach which is used for treating solid tumors of different histologies. Its mechanism is based on the cell membrane permeabilization by means of electroporation.

The main mechanism of electrochemotherapy is to enhance the effectiveness of chemotherapeutic drugs by electropermeabilization, which increases intracellular drug accumulation. Electroporation causes an increased drug uptake of two chemotherapeutics, bleomycin and cisplatin, which are hydrophilic drugs with poor membrane permeability. The presented case shows the treatment procedure for the German boxer dog with a diagnosed mast cell tumor on the lower eyelid.

Two different routes of administration can be used with the electrochemotherapy, intratumoral and intravenous. Cisplatin can be administered intratumorally, whereas bleomycin can be administered intratumorally or intravenously. The concentration of the drugs are low, without systemic side effects.

Applications of electric pulses can be carried out with any generator of electric pulses that produces square-wave electric pulses of appropriate amplitude and duration with adequate frequency. The generator used for the purposes of making this video has an integrated software and a touchscreen interface to select pre-designed electric pulses. It is equipped with a handheld electrode holder with a pulse-activating button attached to the generator by a cord.

Electric pulses are triggered by a foot switch. When injecting the drug intratumorally, the sign of good tissue retention is the tissue whitening. Pay attention to the drug leakage that can occur during the intratumoral injection.

Electric pulses should be applied as quickly as possible in order to obtain the vasoconstricting effect, which contributes to the retention of the drug solution that is injected. A good contact between electrodes and the skin is very essential, which can be assured by depilation and application of water-based gel when plate electrodes are used. Electric pulses are delivered via electrodes that can have different configurations.

Plate or needle electrodes can be used. Its choice is dependent on the tumor location, size, and its thickness. In this case, non-invasive plate stainless steel electrodes with a seven-millimeter distance between the electrodes were used.

Parameters of square-wave electric pulses are set on the touchscreen. Another characteristic of electrochemotherapy is the induction of a vascular lock, or decreased blood flow within the tumor, and consequently the retention of chemotherapeutic drugs within, which can be seen as a mild and brief ischemia. Consequently, due to the vascular disrupting effect, the possible bleeding of the treated tumor is prevented.

The first examination is recommended after one week in order to evaluate the possible local and systemic side effects. After one week, the tumor ulcerated and the area around the tumor was slightly swollen. Follow-up visit after one month serves as an evaluation of treatment response.

Treatment response is dependent on a difference in tumor volume. Therefore, tumor nodules are measured with Vernier caliper and photographed. In four weeks, no evidence of the tumor was noted.

The wound was closed, and cicatrix with alopecia was seen at the treatment site. After treatment, the dog did not show any pain, the function of the eyelid has been preserved during all the healing time, and cosmetic effects after treatment are excellent. Electrochemotherapy can be applied on solitary or multiple cutaneous or subcutaneous tumor nodules with a curative intent or as an adjuvant treatment to surgery.

Electrochemotherapy is effective as one-time treatment only, but in the case of failure or partial tumor response it can be repeated several times with improved effectiveness. In conclusion, the advantages of electrochemotherapy are its simplicity, short duration of treatment sessions, low chemotherapeutic doses, and insignificant side effects. In addition, it is performed on outpatient basis.

Therefore, the patients do not have to stay in the hospital.