[Experimental study of the anti-tumor activity of direct current--an effective adjuvant therapy in irradiation].

The anti-tumor activity of direct current combined with radiation was studied. The experiments were performed with fibrosarcomas (FSA, NFSA) syngenetic to C3H mice. Direct current (0.6mA, 120min) alone was effective to reduce the tumor sizes, but could not cure the tumors. When the direct current therapy (DC therapy) was combined with radiation, the DC therapy following radiation was more effective than that before radiation. Using TCD50 assay, the DC therapy enhanced the effect of a single dose of radiation with the dose-modifying factor of 1.2. However, tumor control rates by the combination therapy were more improved at the smaller doses of radiation than at the larger ones. When the single DC therapy (0.6mA, 120min) was applied immediately after the first radiation of fractionated one the combination therapy still showed the enhanced effect. However, both DC therapy and the radiation therapy were divided in three fractions, and the DC therapy (0.6mA, 40min) was applied after each radiation. Tumor growth retardation by the combination therapy was no different from that by radiation alone. This result suggests that there might be a minimum required dose of coulombs to show the effect of the combination therapy.