Low Percentage of Microenvironment Immune Cells in Bone Marrow and Lymph Node Measured By Flow Cytometry Is Associated with Inferior Overall Survival in Diffuse Large B Cell Lymphoma
Authors: Korin Laura , Fuente Maria Lucia , Cranco Santiago , Ochoa Paola , Vitriu Adriana , Babuin Evelina , Vijnovich Baron Anahí , Venegas Maria Belen , Tempra Paula , Novoa Andrea , Tartas Norma Elisabeth , Custidiano Maria Del Rosario , Foncuberta Maria Cecilia , Sanchez Avalos Julio Cesar 
Published: November 2021

Abstract
INTRODUCTION
Tumor microenvironment (TME) in diffuse large B-cell lymphoma (DLBCL) has recently been in the spotlight. The predictive role of immune cells (IC) in peripheral blood (PB), bone marrow (BM) and lymph nodes (LN) has been individually assessed, often using techniques not widely available. However, data regarding the relative prognostic impact of TME in each compartment evaluated simultaneously in DLBCL is still lacking.
AIMS
To determine the prognostic impact on survival of the monocyte-lymphocyte prognostic score (MLS) in PB and the percentage (%) of IC in the BM and LN measured by flow cytometry (FC) in DLBCL and whether it could improve the conventional risk assessment of the R-IPI.
METHODS
We retrospectively collected information of patients (pts) with DLBCL and available BM aspiration and LN FC data at diagnosis, treated at our center between 2012 and 2019. Pts were stratified according to the MLS (Wilcox et al, Leukemia 2011) in two groups: low (PB monocyte counts &lt;630/ml and lymphocyte counts ≥1000/ml) and intermediate-high risk. FC analysis was performed with 8-color panels according to Euroflow protocols. % of BM and LN IC by FC were compared to normal values determined by Matarraz (Cytometry part B 2010) and Battaglia et al (Immunology 2003), and analyzed in 3 categories: low, normal and high. Survival analysis was performed with Kaplan-Meier (variables compared with log-rank) and Cox regression.
RESULTS
71 pts were included with a median age of 59 years. Table 1 shows frequency analysis of TME variables and R-IPI in our cohort. All pts received immunochemotherapy. Complete remission rate was 82%. Median overall survival (OS) was 120.5 months (m), with a median follow up time of 38.7 m.
On univariate analysis, poor R-IPI and TME variables from the 3 compartments: low LN T lymphocyte (TL) %, both high and low BM monocyte (Mo) %, low polyclonal BM B lymphocyte (BL) %, and intermediate-high MLS showed prognostic impact on OS. BM IC levels did not statistically differ in involved vs not involved BM.
On multivariate analysis, poor R-IPI, low LN TL %, low BM Mo and polyclonal BL, remained independent predictors of survival (Table 2). Pts with the 4 unfavorable variables showed a median OS of only 4 m and 100% mortality rate. In contrast, in pts with none of these adverse risk variables OS rate was 100% (p&lt;0.001), Figure 1.
CONCLUSIONS
Low LN TL %, low BM Mo and polyclonal BL measured by FC were associated with inferior OS in our cohort of DLBCL pts. These TME variables combined with R-IPI can identify both a subgroup of pts with high early mortality rate and a group with excellent long-term prognosis. Immunotherapy with CART cells and BiTEs has shown encouraging results in relapsed refractory DLBCL pts. These strategies could help to improve outcomes in this high risk subset of pts while restoring previously deficient antitumoral immunity.
Figure 1 Figure 1.

Disclosures
No relevant conflicts of interest to declare.