[Failure to partial synchronization with hydroxyurea to improve results of chemotherapy of solid neurosarcoma in the...

Partial synchronization of the slow-growing cell of solid neurosarcoma in the rat can be achieved by blocking DNA synthesis with hydroxyurea. Possible augmentation after synchronization of the therapeutic effects achieved with various cytostatics was tested. The substances were administered to tumour-bearing rats at various times after synchronization (at the transition from G1 to S phase; at maximal DNA synthesis; at the transition from the S to the G2 phases; at mitosis) and therapeutic effects on tumour gs. Cyclophosphamide and adriamycin reduced tumour size, the effect being dose-dependent. No differences were noted between synchronized and non-synchronized cells. Hydroxyurea and vincristine had significantly less effect on the tumour cells, this minimal effect not being enhanced by synchronization. The reported results were obtained in tests on 360 rats and are statistically significant (double variance analysis).