[Radiation sensitizers: with special reference to XXXX cell sensitizers].

@entity1 @entity135 @entity8712 @entity5 @entity26 @entity1432 @entity519 @entity1358 @entity13682 @entity7391 @entity2359
Recent advances in radiation chemistry and radiation biology have led to the combined use of radiosensitizing agents with radiation in the treatment of @entity5 . Various chemicals, including cancerocidal drugs, are used, although radiation sensitizers are defined as drugs which can increase cellular radiosensitivity but have no direct cancerocidal effect. At least four classes of agents, @entity7391 analogues, @entity519 cell sensitizers, PLDR inhibitors and @entity1432 -depleting agents, can modify radiosensitivity and have potential for differential sensitization. @entity7391 analogues are incorporated into DNA in replicating @entity5 cells, and can sensitize these cells to radiation up to a factor of 3. Results of clinical trials of intra-arterial infusion of BUdR have not proved satisfactory, especially with regard to long-term survival, possibly because of the existence of non-replicating cells in the @entity5 . The latter two are still in the experimental stage of study. The radioresistance of @entity519 cells in @entity5 has been regarded as one of the limiting factors in the local control of @entity5 by radiation. Attempts to improve the situation involve high-LET radiation and combined use of chemicals, such as @entity26 , prefluorochemicals and electron-affinic compounds, with low-LET radiation. Although some clinical trials in @entity135 and in cervical @entity5 have yielded positive results in @entity1 treated using hyperbaric @entity26 , attempts have been made to devise other methods, such as those using perfluorochemicals with normobaric @entity26 , because of the technical difficulty involved with the former method. A more promising and easier method is the combined use of electron-affinic chemicals, which like @entity26 can sensitize the @entity519 cells. @entity8712 (alpha @entity13682 derivative) was found to be an excellent sensitizer of this kind in cultured @entity1 cells and in some @entity5 . Several randomized clinical trials to determine its efficacy have been carried out on a word-wide scale, but most of them failed to demonstrate any beneficial effect, mainly because of the drug's @entity2359 which limits its dose. After @entity8712 , many researchers have made every effort to develop more @entity1358 . The present state and future prospects of study were reviewed with special reference to studies currently being undertaken in Japan.
