THE PROGNOSTIC ROLE OF EBV IN PERIPHERAL BLOOD OF PATIENTS WITH DIFFUSE LARGE B CELL LYMPHOMA

Background: The Epstein-Barr virus (EBV) belongs to the herpes virus family\r\nand infects more than 90% of the human population establishing persistent\r\nlatent infection in the host. Although EBV infection is benign in most individuals,\r\nit has been linked to the etiology of a number of lymphoproliferative diseases.\r\n‘EBV-positive diffuse large B-cell lymphoma of the elderly’ was included\r\nas a provisional entity of DLBCL in the revised 2008 WHO classification. We\r\nrecently showed that the plasma EBV-DNA load at HL diagnosis is an indicator\r\nof disease activity and biological characteristics associated with negative\r\nprognosis (Hohaus et al,Clin Cancer Res,2011;17(9); 2885–92).\r\nAims: We studied the role of EBV-DNA copy number in different blood compartments\r\n(whole blood, mononuclear cell fraction, and plasma) in patients\r\nwith DLBCL at diagnosis, as a potential predictive indicator for the presence of\r\nEBV in lymphoma cells and as a prognostic marker in patients treated with\r\nimmunochemotherapy (R-CHOP).\r\nMethods: We analysed 136 patients with DLBCL (median age 62 years, range\r\n15-92 years; 60 females and 76 males). EBV was detected using a commercial\r\nreal-time PCR kit, amplifying a 191 bp region of the EBNA-1 gene (BioQuant\r\nEBV, Biodiversity, Brescia, Italy) in peripheral blood compartments\r\n(whole blood n=133, plasma n=55, and mononuclear cells n=52). Lymph node\r\nsamples from 61 DLBCL patients were analyzed for EBV infection through in\r\nsitu hybridization for EBV-encoded small RNAs (EBER).\r\nResults: EBV was frequently detected in peripheral blood: 35 of 133 whole\r\nblood samples (26%) resulted positive. The copy number varied between 200\r\nand 196000 copies. The presence and copy number of EBV in whole blood and\r\nmononuclear cells were correlated (P<0.05, P<0.01, respectively), while there\r\nwas no correlation to the detection of EBV in plasma. We did not find any association\r\nbetween the presence or viral load of EBV-DNA in any blood compartment\r\nand the presence of EBV in the lymphoma cells of 61 patients studied with\r\nEBER–ISH (11 patients EBER pos). The presence and viral load of EBV in PB\r\nwas not related to age or gender, and other disease characteristics as LDH level,\r\nstage, and IPI. In univariate analysis on 133 patients treated with R-CHOP,\r\nthe presence of EBV-DNA in peripheral blood was associated with a significantly\r\nshorter event-free survival (EFS): 60% versus 79% at 2 years, P<0.04). As\r\nwell, the EBV copy number was correlated with a worse outcome (hazard ratio\r\nof 1.86 for each logarithmic increase; 95% C.I, 1.17-2.97; P<0.009). Correcting\r\nfor IPI in a multivariate Cox analysis, the presence of EBV-DNA in peripheral\r\nblood retained its prognostic significance (hazard ratio 2.02; 95% C.I.,\r\n1.03-3.95; P<0.04).\r\nSummary / Conclusion: Our findings suggest that EBV can be frequently\r\ndetected in peripheral blood at DLBCL diagnosis, which does not reflect the\r\nEBV status of the lymphoma cells, but associates with a worse outcome following\r\nstandard immunochemotherapy. Further studies are needed to explore\r\nthe mechanisms that permit the expansion of EBV-positive cells in peripheral\r\nblood of patients with DLBCL.