Utilization of EBV DNA Copy Number Monitoring in Extranodal NK Lymphoma, Nasal Type in Non Asian Patients

Extranodal NK/T-cell lymphoma, nasal type (ENKL) is a common type of non-Hodgkin's lymphoma (NHL) in Asia and Latin America but is rare in the West. Epstein-Barr Virus (EBV)-encoded RNA (EBER) is detected in most cases of ENKL. Measurement of EBV-DNA copy number (EDCN) in peripheral blood (PB) via polymerase chain reaction (PCR) has been shown in Asian patients to be a useful marker for monitoring tumor burden, response to treatment and disease recurrence (Suzuki, 2011; Ito, 2012), but data in Western patients are lacking. We conducted a pilot, retrospective study of EDCN measurements in Western patients with ENKL, nasal type.

A retrospective review of an IRB-approved patient database identified 13 consecutive patients with ENKL, nasal type, diagnosed between July 1999 and August 2011. Inclusion criteria were based on WHO criteria. Six patients were diagnosed at outside institutions, received initial therapy locally and presented to OSU for evaluation after treatment or at relapse. All pathology specimens were reviewed at OSU. In situ hybridization was used to evaluate EBER expression. PB samples were serially obtained from patients at multiple time points (first visit, longitudinal, last follow up) and analyzed in real time. The Artus™ EBV PCR assay was used for EBV-DNA, extracted from EDTA plasma. 200 uL of patient plasma and 2. 5uL of internal control were processed using the EasyMAG™ sample processor. Quantification of EDCN was done using the EBV TM Master which specifically amplifies a 97bp region of the EBNA-1 gene and the ABI PRISM™ 7500 system. The amplicon was detected by measuring the FAM fluorescence. Quantification of EBV-DNA in the patient's sample was compared to five known standards supplied by Acrometrix. The standards range from 500 to 10, 000, 000 copies/mL. Outcomes including complete response (CR), partial response (PR) and relapse/progression of disease (PD) were assessed according to the Cheson criteria. Categorical data, such as gender, race, stage of disease at diagnosis, number of treatments received and best response were summarized as frequency counts and percentages. Quantitative data, such as age, LDH, WBC, hemoglobin, platelet, were summarized as medians and ranges. Estimates of progression- free survival and overall survival were obtained using the Kaplan-Meier method.

Demographics, pathology, treatment, and outcome data will be provided. For all patients, involved field radiation therapy (IFRT) was part of front line therapy. Figure 1 shows EDCN for 12 evaluable patients. Three patients (1a, 2a, 3a) had elevated EDCN at diagnosis, which normalized with treatment, and remained undetectable at last follow up. All 3 patients achieved CR, 2 patients after initial therapy and 1 patient after allogeneic hematopoietic stem cell transplant (HSCT). Three patients (1b, 2b, 3b) had undetectable EBV-DNA at diagnosis, throughout treatment, and at last follow up. Three patients (1c, 2c, 3c) had no EBV-DNA measurements initially, but all 3 had rapidly increasing EDCN prior to progression and death. Three patients (1d, 2d, 3d), whose disease status and EDCN was documented at multiple time points on long term follow up are analyzed in detail. In patient 1d EBV-DNA was undetectable at diagnosis and at first and second progression, but increased rapidly at third progression and prior to death. Patient 2d had undetectable EBV-DNA at diagnosis, but after front line therapy failure EDCN increased and then closely paralleled clinical response. Following allogeneic HSCT, the EDCN increased rapidly to >10E6 copies/mL, prior to radiographic or clinical evidence of relapse. Patient 3d had elevated EDCN at diagnosis, which normalized with therapy, rose prior to clinically overt first relapse, and normalized again with SMILE chemotherapy.

Elevated EDCN was found in the PB of many non Asian patients with ENKL, nasal type at diagnosis and should be studied prospectively as an adjuvant diagnostic marker, particularly in cases where biopsy is inconclusive or delayed. Serial changes in PB EDCN closely paralleled clinical response in many of the patients. EDCN elevation preceded clinical or radiological evidence of active disease in some patients, prompting further diagnostic work up. The value of serial monitoring of EDCN should be studied prospectively and be included in clinical trials of new therapies for ENKL, nasal type in the U. S.

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No relevant conflicts of interest to declare.