[Radiosensitization research in cancer therapy].

Radiosensitization using Synkavit was first reported by Mitchell in 1953. Recently, renewed interest in radiosensitization has been shown by tumor radiobiologists since electron-affinitive hypoxic cell sensitizers were introduced Adams and his colleagues in 1973. Conferences on chemical modifiers i.e., radiosensitizers and radioprotectors, have been held every two years since 1977 in Britain or North America. At the last meeting in Banff, Canada in 1983 the results of randomized clinical trials of misonidazole were found to be rather disappointing and non-hypoxic cell sensitizers such as halogenated thymine analogues and PLD repair inhibitors were introduced. In parallel with these approaches, hyperthermia research combined with radiation was started in 1974. Very effective radiosensitization by heat-treatment, for example 43 degrees C for 40 min, has been shown in in vitro as well as in vivo experiments. Enhancement of the anti-tumor activity of some chemotherapy drugs using hypoxic cell sensitizers or PLD repair inhibitors was found to be a new approach for improving cancer chemotherapy in 1982. Hyperthermia was also shown to enhance the anti-tumor activity of some chemicals. Thus radiosensitization research may be extended to chemosensitization. i.e., from selective sensitization used in local radiotherapy to that used in systemic chemotherapy.