Plasma EBV Levels as a Prognostic Marker in Patients with Advanced Hodgkin Lymphoma
Abstract & Commentary
By Bindu Kanapuru, MD, Hematology/Oncology Division, IASIA-Falls Church, Falls Church, VA. Dr. Kanapuru reports no financial relationships relevant to this field of study.
Synopsis: In this study, the authors studied the prognostic value of plasma Epstein Barr virus (EBV) DNA levels at diagnosis and 6 months post-treatment in patients with advanced Hodgkin lymphoma treated on the North American Cooperative Intergroup Trial E2496. A cutoff value of 60 copies/100 μL plasma was chosen to stratify samples as EBV(+) OR EBV(-) based on 96% concordance with tissue staining by standard viral nucleic acid (EBER) in situ hybridization (ISH). Plasma EBV positivity prior to treatment as well as at 6 months was associated with significantly shorter failure-free survival (FFS) compared to EBV negative samples. By contrast, no difference in FFS was observed when patients were stratified by EBER-ISH.
Source: Kanakry JA, et al. Plasma Epstein-Barr virus DNA predicts outcome in advanced Hodgkin lymphoma: Correlative analysis from a large North American cooperative group trial. Blood 2013;121:3547-3553.
The gamma herpes Epstein Barr virus (EBV) has been implicated in the pathogenesis of Hodgkin lymphoma. Using standard viral nucleic acid (EBER) in situ hybridization (ISH) on tissue sections, EBV virus has been identified in varying proportions across geographic regions and age groups. In addition, EBV positivity was observed more often in mixed cellularity compared to nodular sclerosis histological sub types.1 EBV genome is also detectable in the serum and plasma of EBV-associated Hodgkin lymphoma patients, as “naked” DNA, rather than virions and can be effectively measured in plasma using polymerase chain reaction (PCR). High degree of concordance was noted between plasma EBV DNA levels and EBER. In addition, higher EBV levels were noted in patients with advanced stage disease, older age in the presence of B-symptoms, and international prognostic score (IPS) > 2.2
In this study, the authors attempted to explore the relationship between plasma EBV DNA and EBV tumor status as measured by EBER-ISH and also evaluated the prognostic value of EBV DNA prior to treatment and at 6 months. There were 116 patients who had both tissue microarray specimens as well as pretreatment blood samples, and these patients were included in the 794-patient Eastern Cooperative Oncology Group–led North American Intergroup study comparing doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD) with the Stanford V regimen (doxorubicin, vinblastine, mechlorethamine, vincristine, bleomycin, etoposide, and prednisone). All patients had either locally advanced disease in the mediastinum or advanced (stage III or IV) histologically proven classical Hodgkin lymphoma.3 The cutoff for plasma EBV-DNA with optimal sensitivity, specificity, and concordance with tumor EBV status by EBER-ISH was determined by a receiver operating characteristic curve and established at > 60 viral copies/100 μL for both pretreatment and 6-month samples. There was no difference between EBV(+) and EBV(-) samples and different age groups, but higher plasma EBV(+) patients were seen in mixed cellularity subtype (24% vs 9%) than nodular sclerosis subtype (43% vs 76%) and patients with higher IPS. At a plasma cutoff level of 60 copies/100 μL, failure-free survival (FFS) was inferior among those with higher EBV-DNA levels (hazard ratio, 2.0; 95% confidence interval, 1.2-3.5; P = 0.01). However, no difference in FFS was noted among EBER-ISH positive or negative samples. EBV(+) remained an independent prognostic factor in multivariate analysis incorporating IPS, histology, and treatment arms. Using the same cutoff value, estimated FFS at 3 years was only 48% in patients whose samples were EBV(+) at 6 months compared to 79% in those who were negative. Median survival was not reached in patients EBV(-) at 6 months (irrespective of pretreatment EBV status) compared to 1.3 years in those who were EBV(+).
Commentary
The authors have shown that pretreatment and 6 months post-treatment EBV(+) status predicts negative outcomes as evidenced by inferior FFS. The ability to identify a molecular marker that can predict clinical outcomes reliably and be easily measured is indeed an important step in the management of Hodgkin lymphoma. Current treatment for Hodgkin lymphoma includes standard radiation or chemotherapy. Several studies have attempted to stratify patients to different therapies using PET scan and clinical and laboratory prognostic scores. Recently, tumor-associated macrophages evaluated by IHC staining for CD68 and CD163 were shown to be associated with inferior FFS.4 Increased CD68 and CD163 expression was associated with positive EBV-encoded RNA. EBV DNA measurement appears to be a unique molecular biomarker5 that can be used to provide prognostic information and, hopefully, ultimately used as a guiding marker in developing personalized therapies for patients with Hodgkin lymphoma.
However, this study was conducted post-hoc and also included only a small sample of total patients in the study (116 of 794). Prospective testing of EBV DNA in Hodgkin lymphoma will be needed before it can be confirmed as an important biomarker for prognostic or predictive purpose.
References
1. Glaser SL, et al. Int J Cancer 1997;70:375-382.
2. Hohaus S, et al. Clin Cancer Res 2011;17:2885-2892.
3. Gordon LI, et al. J Clin Oncol 2013;31:684-691.
4. Tan KL, et al. Blood 2012;120:3280-3287.
5. Meyer RM. Blood 2013;121:3541-3542.