Results of APL 91 European trial combining ATRA and chemotherapy: presentation of APL 1993 trial.

Initial results of ATRA in newly diagnosed APL showed that this drug was associated with a high complete remission (CR) rate but also (i) to a risk of hyperleukocytosis and of ATRA syndrome, (ii) to rapid relapse unless ATRA was followed by intensive chemotherapy. These findings prompted our group to design an approach combining ATRA and intensive chemotherapy in newly diagnosed APL, where chemotherapy could prevent relapses and also, in cases with increasing leukocyte counts, could prevent the ATRA syndrome. In a pilot study, this approach gave a high CR rate (96%) and (with now prolonged follow-up) a significant reduction in the incidence of relapse, as compared to a historical control treated with chemotherapy alone. The superiority of the combination of ATRA and chemotherapy over chemotherapy alone (especially for the incidence of relapse) was subsequently confirmed in a randomized European trial (APL 91 trial). We are now testing in a new European trial (APL 93 trial) whether chemotherapy should be administered with ATRA, or should follow ATRA during induction treatment, and whether maintenance therapy with intermittent ATRA, low-dose chemotherapy, or both can further reduce the risk of relapse.