- Post-consolidation therapy: Patients who do not achieve molecular CR (CRm), but do achieve CR or CRi and are still PML-RARα-positive after consolidation therapy, receive gemtuzumab ozogamicin IV over 2 hours on days 1 and 15. Treatment repeats every 14 days for up to 6 courses or until PML-RARα-negative by PCR. (closed as of 8/15/10)Patients are stratified according to age (18 to 60 years vs > 60 years), acute promyelocytic leukemia (APL) risk group (low vs intermediate), and if the patient received consolidation therapy courses 3 or 4 (yes vs no) regardless of their CRm response. These patients are randomized to 1 of 2 treatment arms. (Randomization and observation arm closed as of 8/15/10) All patients are non-randomly assigned to receive post-consolidation therapy.