All-trans retinoic acid (ATRA)/arsenic trioxide (ATO) combinationbased therapy has benefitted newly diagnosed acute promyelocytic leukemia (APL) in short-term studies, but the long-term efficacy and safety remained unclear. From April 2001, we have followed 85 patients administrated ATRA/ATO with a median follow-up of 70 months. Eighty patients (94.1%) entered complete remission (CR). Kaplan-Meier estimates of the 5-year event-free survival (EFS) and overall survival (OS) for all patients were 89.2% ؎ 3.4% and 91.7% ؎ 3.0%, respectively, and the 5-year relapse-free survival (RFS) and OS for patients who achieved CR (n ‫؍‬ 80) were 94.8% ؎ 2.5% and 97.4% ؎ 1.8%, respectively. Upon ATRA/ATO, prognosis was not influenced by initial white blood cell count, distinct PML-RAR␣ types, or FLT3 mutations. The toxicity profile was mild and reversible. No secondary carcinoma was observed, and 24 months after the last dose of ATRA/ATO, patients had urine arsenic concentrations well below the safety limit. These results demonstrate the high efficacy and minimal toxicity of ATRA/ATO treatment for newly diagnosed APL in long-term follow-up, suggesting a potential frontline therapy for de novo APL.combination therapy ͉ 5-year EFS ͉ 5-year OS ͉ residual disease ͉ arsenic retention A cute promyelocytic leukemia (APL) is the M3 subtype of acute myeloid leukemia (AML) and is characterized by an accumulation of abnormal promyelocytes in the bone marrow and a severe bleeding tendency. Additionally, in the great majority of cases, APL is associated with the t(15,17) chromosomal translocation and resultant PML-RAR␣ transcripts that encode the leukemogenic PML-RAR␣ fusion protein (1). Five decades ago, APL was the most fatal type of acute leukemia and was considered essentially untreatable (2). The first breakthrough came with the use of anthracyclines, which improved the complete remission (CR) rate but provided a low 5-year overall survival (OS) (3). The introduction of all-trans retinoic acid (ATRA) therapy resulted in terminal differentiation of APL cells and a 90-95% CR rate in patients (1, 4), and subsequent combination of ATRA with chemotherapy raised the 5-year disease-free survival (DFS) rate up to 74% (5). In the 1990s, significant benefits of arsenic trioxide (ATO) were reported, which further improved the outcome of patients with APL (6, 7). ATO exerts dose-dependent dual effects on APL cells, with low concentrations inducing partial differentiation and relatively high concentrations triggering apoptosis. Of note, both ATRA and ATO induce catabolism of the PML-RAR␣ fusion protein, demonstrating a paradigm for rationally targeted therapy in leukemia. However, between 20% and 30% of newly diagnosed APL patients treated with regimens based on the use of ATRA or ATO as single agents will develop disease recurrence or drug resistance.To improve further the clinical outcome of APL, therapeutic strategies should be designed to include combinatorial use of drugs with distinct but convergent mechanisms that may amplify treatment effic...