Tumour treatment by direct electric current: electrode material deposition

Direct current electrotherapy was demonstrated to be an effective and relatively inexpensive local treatment of murine solid subcutaneous tumours. The insufficient knowledge of the mechanisms involved hinders its more extensive use in clinical oncology. Attempts were made to establish the correlation between the effectiveness of electrotherapy and deposition of the electrode material in the tumours. Electrotherapy was performed as a 1 h single-shot treatment in different electrode (gold) configurations, one electrode inserted in the tumour being the anode and its pair subcutaneously in the vicinity of the tumour being the cathode, and vice versa, and with both electrodes placed subcutaneously in the tumour vicinity. Tumour growth and the amount of electrode material in tumours were determined at different times after single-shot electrotherapy with gold needle electrodes. Different electrode configurations were employed with respect to tumours at the same current level and different current levels were used in the same electrode configuration. The amount of gold deposited in the tumour was observed with respect to tumour response to electrotherapy. Tumour growth after 0.6 rnA direct current electrotherapy was significantly retarded with respect to controls regardless of the electrode configuration, with no significant differences among them. The amount of gold per tumour, however, varied significantly with the electrode configuration. In the experiments in which both electrodes were placed subcutaneously outside the tumour, increasing current intensities produced a "dose" -dependent tumour growth response to electrotherapy which was not related to the amount of gold found in the tumours. The results obtained in this study showed that the electrode material deposition (gold) and possibly consecutive metal toxicity were not the major mechanism involved.