Clinical, Immunophenotypic and Genetic Characteristics of Aggressive (non-Burkitt) B-Cell Lymphoma in a Real Life Cohort

Introduction: Diffuse large B-cell lymphoma (DLBCL) is an aggressive and heterogeneous disease characterized by recurrent genetic alterations. Several adverse prognostic factors are well known as International Prognostic Index (IPI) parameters or MYC and BCL2 and/or BCL6 gene rearrangements (High-Grade B-cell Lymphoma double/triple hit, HGBL-DH/TH, according to the 2016 WHO classification). Other factors are controversial as previous history of indolent lymphoma, cell of origin (COO), co-expression of MYC and BCL2 proteins (double expressor (DE) status), MYC partner gene if rearranged. The aim of this study is to describe a « real life » cohort of patients treated in our institution for aggressive (non-Burkitt) B-cell lymphoma and to evaluate the prognostic impact of phenotypic and genetic alterations.

Methods: We collected clinical and histological characteristics of patients uniformly treated between January 2009 and June 2017 with rituximab R-CHOP/CHOP-like chemotherapy. Treatment was reinforced with high dose methotrexate in case of central nervous system (CNS) localization or HGBL subtype. All tumor samples were analysed for MYC and BCL2 protein expression by immunohistochemistry. BCL2, BCL6 and MYC break were analysed by Interphase Fluorescence In Situ Hybridization (FISH) with breakapart probes. When MYC was rearranged MYC partner gene was analysed with double fusion probes (MYC/IgH, MYC/IgL, MYC/IgK). Positron Emission Tomography (PET scanner) was performed with maximal Standardized Uptake Value (SUV max) at baseline in all patients except 7.

Results: 242 patients were studied. Baseline characteristics were: median age: 61 y (18-88), IPI 3-5: 49.6%, CNS localization: 6.6%. With a median follow-up of 4.4 years, 5y-overall survival (OS) and 5y-progression free survival (PFS) were 72% (66.0-78.5) and 65% (58.5-71.3), respectively. SUV max at baseline was 17,1 (minimum value 2,4 - maximal value 39,3).Histological diagnoses were DLBCL-not otherwise specified (NOS): 57%, transformed DLBCL: 26%, HGBL: 7.9%, primary mediastinal B-cell lymphoma (PMBL): 4.1% and others: 5%. Using Hans algorithm, 48.8% were classified as germinal center (GC), 47.9% as non-GC, 3.3% could not be evaluated and 38% were DE. MYC rearrangement was detected in 36 cases (14.9%) with an immunoglobulin partner gene (IgH, IgL or IgK) in 24 (77.4%) of 31 evaluable cases. BCL2 and BCL6 rearrangement were observed in 45 cases (18.6%) and 62 (25.6%) cases respectively. Fifteen cases were HGBL DH/TH including 7 DH MYC/BCL2, 5 DH MYC/BCL6 and 3 TH MYC/BCL2/BCL6. Four cases were HGBL-NOS. IPI score 3-5 (p<0.0001) and HGBL (p=0.03) were significantly associated with inferior OS. IPI score 3-5 (p<0.0001), DE status (p=0.03), MYC-R (p=0.05) and BCL2-R (p=0.0014) were significantly associated with inferior PFS. Previous indolent lymphoma, COO and MYC partner gene had no impact on OS or PFS.

Conclusions: This monocentric study in a large cohort of aggressive B-cell lymphoma patients treated in real life conditions confirms previous reports on the negative prognostic impact of DE status, MYC and BCL2 translocations and HGBL subtype. These genetic and immuno-histological characteristics should have implications in the design and interpretation of future clinical trials.