Prognostic Impact of Bone Marrow B Lymphocyte Precursors (hematogones) Detection in 95 Acute Lymphoblastic Leukemia Cases
Authors: Chantepie Sylvain P , Dugué Audrey Emmanuelle , Chevallier Patrice , Schmidt-Tanguy Aline , Salaün Véronique , Garand Richard , Eveillard Marion , Reman Oumedaly 
Published: October 2019

Abstract
Abstract 4791
Acute lymphoblastic leukemia (ALL) multiparameter flow cytometry (MFC) study of bone marrow aspiration after chemotherapy is crucial for determining minimal residual disease (MRD). Hematogones (HGs) have to be distinguishing from leukemic cells in B-cell subtypes and could be quantify during follow-up. To date, the incidence of Hgs in ALL and their prognostic significance have not been investigated. The aim of this multicenter study was to quantify Hgs after chemotherapy in ALL adult patients and to define its prognostic value.
We retrospectively analyzed the incidence of HGs in 95 ALL patients, 71 with B-ALL (75%), 24 (25%) with T-ALL in first line treatment. The median age was 37 years [8–71], 20% had t(9;22) cytogenetic abnormality, and 70% had abnormal karyotype. 4/5-color MFC analysis MRD and HGs were performed at different time point (TP) after diagnosis: TP1 (post-induction, day 45 [41–61], n=78), TP2 (post-consolidation, day 111 [94–144] 25, n=42), TP3 (post-intensification/before hematopoietic stem cell transplantation (HSCT), day 179 [125–268], n=58), TP4 (n=11), TP5 (n=17), TP6 (n=9) after a median of 33, 91 and 167 days after HSCT, respectively. A total of 39 patients (41%) relapsed with a median of 26 months [7.7–47.9]. Forty seven patients (50%) received an HSCT in a complete (98%) or partial remission (2%). At TP1, TP2, TP3, TP4, TP5, TP6, the median HGs [range] were as followed: 0.00 [0.00–6.90]%, 0.30 [0.00–11.2]%, 0.98 [0.00–33.00]%, 0.52 [0.00;23.00]%, 5.50 [0.00;25.00]%, 4.60 [0.00;34.00]%, 5.90 [0.32;11.80]%, respectively. Figure 1 showed the percentage of patients with negative MRD (Figure 1A) and detectable HGs (figure 1B) during the follow up of ALL patients. There is a progressive increase of the percentage of patients with detectable HGs during the time of treatment and follow-up.
Interestingly, there was no correlation between age and HGs level while in physiological situation the HGs rate decreases with increasing age. There was a negative correlation between positive MRD and detectable HGs at TP1 (p=0.022) but not at TP3 (p=0.88). In univariate analysis positive MRD at P1 and P3, age (/10), the presence of t(9;22) and absence of HGs at TP3 (figure 2) were bad prognostic factors for relapse free-survival (RFS) and overall survival (OS). The presence of HGs at other different time of evaluation was not associated with a significant decrease of relapse or death. However, patients who had a negative MRD at TP1 and detectable HGs in the bone marrow at TP3 exhibited a better RFS and OS (p=0.018 and p=0.065 respectively). Patients who had negative MRD at TP3 and had detectable HGs at TP3 had also a better RFS and OS (p=0.007 and p=0.011, respectively) compared to patients with negative MRD at TP3 and without HGs (figure 3). In patients who had a positive MRD at TP1, detectable HGs at TP3 identified a subgroup of patient with favorable OS compared to patient with positive MRD at TP1 and without detectable HGs (p=0.072).
These results should be taken with cautious because of the decreasing number of patients evaluated at different time points. However, HGs analysis could represent a new area of investigation in search of new prognostic factors in the context of adult ALL.
Figure 1. Percentage of patients with (A) negative MRD and (B) detectable HGs at different time points after starting of treatment. Figure 1. Percentage of patients with (A) negative MRD and (B) detectable HGs at different time points after starting of treatment.
Figure 2. Overall survival according to HGs status at TP3. Figure 2. Overall survival according to HGs status at TP3.
Figure 3. Overall survival in patients with negative MRD at TP3 according to HGs status. Figure 3. Overall survival in patients with negative MRD at TP3 according to HGs status.

Disclosures:
No relevant conflicts of interest to declare.