Risk-adapted treatment of acute promyelocytic leukemia with all-trans-retinoic acid and anthracycline monochemotherapy: a multicenter study by the PETHEMA group.

All-trans-retinoic acid (ATRA) increases the efficacy of chemotherapy when used for induction and maintenance treatment of acute promyelocytic leukemia (APL), but its role in consolidation is unknown. Since November 1996, 426 patients with newly diagnosed APL have received induction therapy with ATRA and idarubicin. Before November 1999 (LPA96 study), consolidation therapy consisted of 3 courses of anthracycline monochemotherapy. After November 1999 (LPA99 study), patients with intermediate and high risks of relapse received consolidation therapy with ATRA and increased doses of anthracyclines. Of the 384 patients who achieved complete remission (90%), 382 proceeded to consolidation therapy. Seven patients died in remission (1.8%). The 3-year cumulative incidence of relapse for patients in the LPA96 and LPA99 studies was 17.2% and 7.5%, respectively (P =.008). Patients treated with ATRA in consolidation therapy showed an overall reduction in the relapse rate from 20.1% to 8.7% (P =.004). In intermediate-risk patients the rate decreased from 14.0% to 2.5% (P =.006). This improved antileukemic efficacy also translated into significantly better disease-free and overall survival. A risk-adapted strategy combining anthracycline monochemotherapy and ATRA for induction and consolidation therapy of newly diagnosed APL results in improved antileukemic efficacy and a high degree of compliance.