[The effect of cyclophosphamide on tumors in the sensitivity-test (author's transl)]

The sensitivity of tumors to cyclophosphamide was tested in vitro. For this purpose, the urine of cyclophosphamide-treated rats (90 min., 500 mg/kg) was used. This method of activating cyclophosphamid proved more advantageous than other methods; all cytostatically effective metabolites can be used in the test and the production of metabolites can easily be standardized. Consequently results with good reproducibility can be obtained. In various long-term and short-term test models with animal transplantation-tumors in vitro, the effects of the cyclophosphamide metabolites depended on the dose used. This test results in the various test models are comparable. In the tissue-culture of tumors (long-term test) sensitivity was evaluated by using morphological criteria as well as by counting cell numbers. In the short-term test the sensitivity of tumors was found out by influencing the nucleic acid syntheses (3-H-thymidine-, 3-H-uridine-incorporation). As the tissue-culture meets with difficulties as a routine clinical examination, the use of the short-term test is recommended. Using as model the fast proliferating WALKER-256-carcinosarcoma and a slowly proliferating rat adenocarcinoma, the results of the sensitivity-test in vitro were compared with the effects of therapy in animal tests. Tumor remissions corresponding with the results reached in vitro, which depended on dosis, could also be achieved in both transplantation-tumors. Human tumors, tested in in vitro studies (short-term-test), show a different sensitivity to cyclophosphamide.