Mathematical modelling of physicochemical reactions and transport processes occurring around a platinum cathode during the electrochemical treatment of tumours

The electrochemical treatment (EChT) of tumours is an anti-tumour therapy in which a continuous direct current is applied to electrodes, placed in or near a tumour. Promising results have been reported from clinical trials in China, where more than 10,000 patients have been treated with EChT during the past 10 years. Before clinical trials can be conducted outside of China, a reliable dose-planning strategy has to be developed. One approach in achieving this is the use of physicochemical simulation models. A simplified mathematical model of the physicochemical processes, occurring around a spherical platinum cathode during EChT, is developed and visualized in three steps in this paper. In the final step, tissue is treated as an aqueous solution of sodium chloride, containing a bicarbonate buffer system and organic constituents susceptible to reactions with hydroxyl ions. This model is shown to give a good description of the pH profile obtained around the cathode after EChT. The simulation results reveal a strong correlation between the pH profiles and size of experimentally measured lesions, thus indicating that it is the spreading of hydroxyl ions that determines the extent of tissue destruction around the cathode. In addition, the simulations indicate that the model could be of use in predicting the size of a lesion produced by EChT.