AML-430: Utility of End-of-Induction Bone Marrow Biopsy in APL Patients Treated with ATRA/ATO Regimen

Background: Significant variations exist related to end-of-induction (EOI) practices in APL management. These include fixed dose/duration ATRA/ATO vs continuation of ATRA/ATO until hematologic complete remission (CR) and performance vs omission of EOI bone marrow biopsy (BMBx) to confirm CR. These variations arise from the original protocols (notably, APL0406), as well as ELN-2019 and NCCN-2020 guidelines. Objectives: To assess utility of EOI BMBx morphologic findings in APL patients treated with a 28-day ATRA/ATO induction regimen. Methods: Patients ≥ 18 years treated for APL with ATRA/ATO ± cytoreductive agent at a tertiary center from 12/2012 to 03/2020 were identified. Patients who received >30 doses of ATO or those who died in the first 4 weeks of treatment were excluded. Demographics, hematologic parameters, treatment details, and BMBx results were collected. Time-to-event endpoints were calculated from day 1 of ATO. Results: Sixty-one patients (42 low/intermediate-risk, 19 high-risk) were included in the study. Median age at diagnosis was 51 years (21–81 years); 47 (77%) were Caucasian. No low/intermediate-risk APL patients received gemtuzumab ozogamicin (GO); 2 received anthracycline. Five high-risk APL patients received GO; 10 received anthracycline. Median time-to-dose 28 ± 2 of ATO was 28 days (27–40). Day 28 hematologic parameters showed that 38 (62.3%) patients had ANC Conclusions: A 28-dose fixed ATO-containing ATRA/ATO regimen delivers excellent outcomes. Our data suggest that EOI-BMBx can be safely omitted, irrespective of hematologic parameters.