Post-Transplant MRD Negativity on Day +100 Predicts Outcomes for Pre-Transplant Relapsed/Refractory AML Patients
Authors: Klyuchnikov Evgeny , Badbaran Anita , Massoud Radwan , Fritsche-Friedland Ulrike , Christopeit Maximilian , Janson Dietlinde , Ayuk Francis A. , Wolschke Christine , Kröger Nicolaus 
Published: November 2021

Abstract
Introduction
Patients with relapsed/refractory (r/r) AML have in general a dismal prognosis. Allogeneic stem cell transplantation (allo-SCT) provides a curative approach for these patients, however the overall survival (OS) remains still low achieving 20-40%. Though post-transplant minimal residual disease (MRD) monitoring has been shown to be predictive for development of post-transplant relapses and lower survival, data focusing on pre-transplant relapsed/refractory AML patients is scarce. In this study, we investigated the impact of achieving MRD negativity on day +100 for relapses and survival for this high risk patients.
Patients and Methods
We analyzed post-transplant outcomes for pre-transplant r/r AML patients depending on their post-transplant MRD status at day +100. The day +100 was chosen concerning the possibility of early post-transplant interventions (e.g. tapering of immunosuppression or administration of donor lymphocytes).
Fifty six consecutive adult patients (≥18 years old) with r/r AML (median age 58, range 20-76; male, n=34, 61%) who underwent allo-SCT (first, n=44, 79%; second, n=12, 21%) between 2015-2020 at the Department for Stem Cell Transplantation at the University Medical Center Hamburg (Germany) were included. The MRD was assessed on day +100 using multiparameter flow cytometry according to "different from normal" strategy.
The patients experienced rather primary refractory disease (64%), secondary/therapy-related AML (55%) and abnormal cytogenetics (59%) at diagnosis. The median pre-transplant blast count was 25% (6-91%). A number of 29 patients (52%) showed blasts in peripheral blood. Myeloablative conditioning was used in 31 (55%) patients, whereas 25 (45%) patients received reduced intensity regimens. A number of 29 patients (52%) received a FLAMSA-based conditioning. Post-transplant donor lymphocyte infusions as well as other treatment were given to 13 (23%) and 17 (30%) patients, respectively.
Results
The median follow up was 20 months (range 4-66). Forty patients (71%) achieved MRD negativity on day +100 and 16 (29%) remained MRD positive. The 2-year OS, LFS, relapses and NRM at 2 years for day +100 MRD negative patients were: 76% (95% CI: 60-87%), 59% (95% CI: 41-75%), 31% (95% CI: 17-50%) and 8% (95% CI: 3-19%), respectively. The 2-year OS, LFS, relapses and NRM at 2 years for day +100 MRD positive patients were: 35% (95% CI: 17-59%, p=p=0.001), 23% (95% CI: 9-46%, p&lt;0.0001), 70% (95% CI: 45-87%, p=0.0002) and 6% (95% CI: 1-28%, p=0.88), respectively.
Several factors were evaluated for possible association with day +100 MRD negativity (Table 1). There were no significant associations. Further, the incidence of acute (grade II-IV) GvHD at 100 days was not significantly different between the day 100 MRD positive und negative patients.
Following factors had impact on post-transplant outcomes in multivariate analysis: presence (no vs yes) of peripheral blasts prior to allograft (OS: HR 0.3, 95% CI: 0.1-0.9, p=0.03; LFS: HR 0.4, 95% CI: 0.1-0.9, p=0.03; relapses: HR 0.4, 95% CI: 0.1-0.99, p=0.048; NRM: HR 0.5, 95% CI: 0.2-1.3, p=0.17), FLAMSA vs other preparative regimens (OS: HR 0.4, 95% CI: 0.1-0.93, p=0.03; LFS: HR 0.4, 95% CI: 0.2-0.98, p=0.04; relapses: HR 0.4, 95% CI: 0.2-1.0, p=0.05; NRM: HR 0.4, 95% CI: 0.2-1.0, p=0.06), and day +100 MRD (negative vs positive) (OS: HR 0.3, 95% CI: 0.1-0.7, p=0.009; LFS: HR 0.2, 95% CI: 0.1-0.6, p=0.001; relapses: HR 0.2, 95% CI: 0.1-0.4, p=0.0001; NRM: HR 0.2, 95% CI: 0.1-0.5, p=0.0006).
Conclusions
Post-transplant MRD detection plays predictive role in pre-transplant r/r AML patients and may help to define possible candidates for early post-transplant interventions.

Disclosures
No relevant conflicts of interest to declare.