[Experimental study of transvascular direct current treatment for intraabdominal malignant tumors]

Direct current treatment (DCT) is a treatment for malignant tumors suggested by Nordenström in 1978. In DCT, two platinum electrodes, an anode and a cathode, are introduced percutaneously. Usually the anode is inserted into the tumor, and the cathode is inserted into healthy tissue near the tumor. Passage of a direct current acidifies the surroundings of the anode and causes necrosis of this part of the tumor. DCT has been used to treat lung cancer and superficial tumors clinically, but it has not yet been used for intra-abdominal tumors. Here, basic and experimental studies were made of the possibility of DCT of intra-abdominal tumors. A modification, called transvascular DCT, was done with the anode inserted into the liver of rabbits and the cathode placed within a blood vessel by vascular catheterization. First, tests were done to identify a suitable material for the cathode, from the standpoint of safety. DCT is usually done with platinum electrodes. However, in transvascular DCT, platinum could not be used for the cathode because with its use, hydrogen gas was produced in the vessel, causing embolisms. So, a cathode made of AgCl and coated with Ag was developed to prevent embolism. With this cathode, gas was not generated. Next, pathological changes in the walls of the vessel that contained the cathode were observed after DCT. The cathode was put into a tube placed in the inferior vena cava (IVC) or the aorta. a. IVC: A histological study done immediately after DCT showed an area of necrosis in the wall of the IVC in all 19 rabbits. A study done 7 days after DCT showed damage in the IVC wall of all five animals examined. b. Aorta: A histological study done immediately after DCT showed a small edematous area in the wall of the aorta in seven of the 22 animals, and no evidence of any damage in the other 15. A study done 7 days after DCT showed no damage in any of the 16 animals. The aorta was more suitable for use as the vessel to contain the cathode than the IVC, because injury of its wall was minor and reversible. Thus, transvascular DCT could be done safely by use of an Ag-coated cathode made of AgCl and placed in the aorta.