Pilot study of all-trans retinoic acid as post-remission therapy in patients with acute promyelocytic leukemia.

Chemotherapy may decrease relapses of acute promyelocytic leukemia (APL) following induction with all-trans retinoic acid (ATRA), however the optimal timing of these two modalities remains to be determined. We treated eight patients with morphologic evidence of APL with intensive induction chemotherapy followed by ATRA (45 mg/m2/d for 10 weeks). All eight patients achieved a complete remission following chemotherapy. After a median follow-up of 29.0 months, seven patients remain in complete remission; one patient relapsed at 26.9 months. RT-PCR analysis for the PML/RAR alpha rearrangement was performed to monitor patients for evidence of minimal residual disease. Both of the patients with persistence of this rearrangement after induction chemotherapy converted to negative following ATRA. Toxicity of ATRA given in the post-remission setting was mild and consisted of headache, dry skin, and elevations of triglycerides and transaminases. No patient developed evidence of the retinoic acid syndrome. The administration of ATRA after intensive induction chemotherapy is associated with durable remissions and minimal toxicity in patients with APL. Disappearance of the PML/RAR alpha rearrangement after ATRA suggests that ATRA is effective against minimal residual disease.