COMPARABILITY OF RESULTS OF POSTNATAL AND LONG-TERM TESTS FOR CARCINOGENICITY

A method of testing postnatal carcinogenicity in rats was elaborated. The substances to be tested were administered from the 1st day after b irth to the 5th, 10th and 20th days of age. The subsequent supply of a substance in diet from weaning (28th day of age) up to the end of the first year of survival was an optimal combination. A total of 12 subs tances were tested by this method. For all substances it was possible to provide a comparison with the results of long-term studies. For nin e substances carcinogenicity was demonstrated in both tests, out of th em in eight cases in identical organ systems. In three cases no carcin ogenicity was ascertained in the postnatal study, in two compounds ide ntical negative results were obtained by the two approaches. In one ca se (the cytostatic TS-160) development of sarcomas was found at the si te of subcutaneous administration in the long-term study, and this eff ect was not observed in the postnatal study. Results identical for the two methods (carcinogenic or noncarcinogenic) were achieved in 11 sub stances, i.e. 91.7%. In addition, in 10 compounds, for which carcinoge nicity was demonstrated either in the postnatal study or in the long-t erm study, the occurrence of tumors was found in identical organ syste ms after 8 compounds which is an 80% agreement in mice, this identity of organs was demonstrated only in 62.5% of the compounds tested. The present results demonstrated that the use the postnatal carcinogenicit y lest in rats offers the determination of possible carcinogenic effec t of the compound tested with a high probability, under economically m ore advantageous conditions, and with almost the same qualitative resu lts as with the use of the long-term tests for carcinogenicity.