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Abstract:
The cytotoxic action of ionizing radiation can be increased by cis-platinum (CDDP) and its derivates. This effect is due to interactions in the cellular desoxyribonucleic acid (DNA), and it is especially marked in a hypoxic medium. A synergistic and an additive summation can be discerned depending on the type and dosage of the applied substance and the temporal relation between its application and irradiation. The radiosensitization of DNA before radiotherapy (RT) and the restriction of recovery processes after RT are considered as main mechanisms of this effect. A therapeutic potentialization of CDDP and RT could be demonstrated in a series of experimentations on animals. E.G. a therapeutic gain factor of 1.7, related to the sound surrounding tissue, was found out for the C3H mammary carcinoma during a series of in-vivo experimentations on mice. The applicability of a simultaneous treatment with CDDP and RT of human tumors depends on the systemic and local side effects of such a therapy. The results achieved hitherto in clinical pilot studies on advanced solid tumors situated above all in the head and neck area are at least equivalent to those of a sequential induction chemotherapy and subsequent definitive radiotherapy. They can possibly be improved by a further optimization of the temporal application and dosage of CDDP, but also by using other platinum derivates. It is not yet possible to describe any undesired long-term effects. However, the side effects observed hitherto in the irradiated areas are apparently of minor clinical importance.