TUMOR 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 tu mours. The insufficient knowledge of the mechanisms involved hinders i ts more extensive use in clinical oncology. Attempts were made to esta blish the correlation between the effectiveness of electrotherapy and deposition of the electrode material in the tumours. Electrotherapy wa s performed as a 1 h single-shot treatment in different electrode (gol d) configurations, one electrode inserted in the tumour being the anod e and its pair subcutaneously in the vicinity of the tumour being the cathode, and vice versa, and with both electrodes placed subcutaneousl y in the tumour vicinity. Tumour growth and the amount of electrode ma terial in tumours were determined at different times after single-shot electrotherapy with gold needle electrodes. Different electrode confi gurations were employed with respect to tumours at the same current le vel and different current levels were used in the same electrode confi guration. The amount of gold deposited in the tumour was observed with respect to tumour response to electrotherapy. Tumour growth after 0.6 mA direct current electrotherapy was significantly retarded with resp ect to controls regardless of the electrode configuration, with no sig nificant differences among them. The amount of gold per tumour, howeve r, varied significantly with the electrode configuration. In the exper iments 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 stud y showed that the electrode material deposition (gold) and possibly co nsecutive metal toxicity were not the major mechanism involved.