# Fludarabine melphalan reduced intensity conditioning vs radiation-based myeloablative conditioning in patients undergoing allogeneic transplantation for acute myeloid leukemia with measurable residual disease

## TL;DR

This study compares two conditioning regimens for allogeneic transplants in AML patients with residual disease, finding similar outcomes between them.

## Contribution

The study provides evidence that FluMel is a viable alternative to MAC for MRD+ AML patients ineligible for MAC.

## Key findings

- MRD+ patients had significantly lower survival and higher relapse rates compared to MRD− patients.
- No significant difference in outcomes was found between MAC and FluMel in MRD+ patients.
- FluMel is a reasonable option for MRD+ patients who cannot undergo MAC.

## Abstract

Patients with AML and measurable residual disease (MRD) undergoing allogeneic hematopoietic cell transplantation (HCT) may benefit from myeloablative conditioning (MAC) when feasible to reduce relapse risk. Fludarabine-Melphalan (FluMel) is a common reduced intensity conditioning (RIC) regimen; however, data in MRD+ patients is sparse. We performed a retrospective review of AML patients who underwent their first HCT (2016–2021) without morphologic disease at City of Hope who had pre-transplant marrow evaluated for MRD using multicolor flow cytometry (MFC) and received radiation-based MAC or FluMel conditioning. We identified 312 patients; 44 with MRD+ disease pre-HCT. The 24-month overall survival (OS), leukemia-free survival (LFS) and cumulative incidence of relapse (CIR) were 47.7%, 40.9%, and 38.6% in MRD+, and 78.0%, 73.9%, and 14.6% in MRD− patients. Radiation-based MAC was given to 136 (43.5%) patients (n = 20 with MRD+) and FluMel was given to 174 (55.8%) patients (n = 24 with MRD+). In patients with MRD+, there was no statistically significant difference between those who received MAC vs. FluMel in 24-month OS (60% vs. 38%, p = 0.21), or CIR (35% vs. 42%, p = 0.59), respectively. Our data substantiates the adverse impact of MRD in patients with AML undergoing HCT; FluMel is a reasonable option for MRD+ patients unfit for MAC.