Prediction of the response to chemotherapy in acute leukemia.

The prognostic value of the in vitro incorporation of labeled thymidine was evaluated in 53 cases of acute leukemia, by means of autoradiography and liquid scintillation (LS) count. A higher rate of incorporation before therapy with higher labeling index and LS- specific activity was observed in patients who later responded to chemotherapy with a complete remission. The in vitro depression of labeled thymidine incorporation after incubation with the two drugs selected for the induction therapy was more marked in those who responded to therapy than in the nonresponders. The in vitro incorporation of 3H-thymidine was also evaluated after 48 hours of chemotherapy ("vivo-vitro" test). A decrease of the incorporation was observed frequently in the responders. On the other hand, in the group of nonresponders, there was generally an increase of the incorporation measured by the liquid scintillation count, often contrasting with a decrease of the labeling index, and corresponding to a higher rate of intracellular incorporation. The prognostic value of these findings appears to be significant, as it allows the response to chemotherapy to be predicted, as well as allowing the selection of the various cytotoxic drugs.