[Relationship of the antitumor action of cyclophosphamide and prednisolone to the sequence of their administration and to the intervals between administrations in methylcholanthrene carcinogenesis in mice].

The relationship of the antitumor action of cyclophosphamide combined with prednisolone and sequence of and intervals between administrations was studied in C57Bl/bj mice at methylcholanthrene cancerogenesis. Administrations of the drugs was started from the 50th day of cancerogenesis. The best results were obtained in an experiment where the first cycloion of prednisolone. Under these circumstances half of the animals did not develop tumours. Meanwhile the tumours that arose had low tempoes of the growth and tumour-bearing animals showed the longest life span. With an increase in the interval between prednisolone treatment onset and cyclophosphamide injection, the therapeutic effect of the combination declined that was manifested by all the parameters. An opposite effect was recorded in chronic administration of prednisolone following preliminary injections of cyclophosphamide. An increase in the interval between administration of the drugs enhanced therapeutic efficacy of the combination.