Antitumor effect of thermodifferential chemotherapy with carboquone on Ehrlich carcinoma

A thermodifferential chemotherapy, consisting of systemic administration of antitumor drug and local hyperthermia combined with general hypothermia, was examined and gave satisfactory antitumor results. In search of basic optimal conditions required, this therapeutic system was tested on Ehrlich tumor implanted in the hind limbs of mice. The results obtained were as follows: (a) From the viewpoint of either the antitumor effect or the adverse effect of the therapy, local hyperthermia at 41 degrees for 60 min combined with general hypothermia at 20 approximately 24 degrees was found to be the best thermodifferential condition. (b) The thermodifferential treatment alone without drug administration displayed little antitumor effect. (c) General hypothermia applied not only enhanced the antitumor effect of the drug in loco but also reduced general toxicity of the drug. In the present therapy, carboquone displayed the best antitumor effect among the drugs tested. This suggests that the potentiation of tumoricidal activity of carboquone under the acidic condition produced by cancer cell metabolism in hyperthermia was deeply involved in the effectiveness of this therapy.