Peripheral blood of patients with extranodal NK/T-cell lymphoma, nasal type (ENKL) contains fragmented Epstein-Barr virus (EBV) DNA. Measurement of the circulating viral DNA load has been reported to be useful for the diagnosis, monitoring and prognostication of the disease. However, there are two different subjects for analysis, plasma/serum component and mononuclear cells (MNC). Most reports do not compare both samples from the same patients, and are biased by a retrospective manner of accrual. Therefore, it remains unclear which samples are more useful subjects.
To evaluate clinical significance of peripheral blood EBV-DNA copy number for ENKL, we conducted a prospective study to analyze EBV-DNA with quantitative polymerase chain reaction. Inclusion criteria are as follows: (1) Diagnosis of ENKL or aggressive NK-cell leukemia by biopsy or cytology. (2) Patients without other serious complications and those tolerable for chemotherapy and/or radiotherapy. (3) No prior history of chemotherapy or radiotherapy. (4) Patients with written informed consent. Primary endpoint was a prognostic value of EBV-DNA copy number to predict 2-year overall survival. Secondary endpoints were comparison of EBV-DNA copy number and pretreatment characteristics and prognostic capability of EBV-DNA during/after treatments. Three times of analysis, pre-treatment, mid-treatment, post-treatment, at central laboratory was to be performed for each patient.
A total of 33 patients were registered from June 2004 to March 2007. All patients were diagnosed with ENKL and male/female ratio was 21/12. The median age was 56 years old, ranging from 18 to 81. 19 patients were in stage IE, 3 in stage IIE, and 11 in stage IV. 13 patients had B-symptom and 14 had elevated serum LDH level. ECOG performance status was low (0–2) in 29 patients, but was 3 in 2 patients. IPI was high-intermediate/high in 11. First line treatment included concurrent chemoradiotherapy in 16, radiotherapy followed by chemotherapy in 8, and chemotherapy alone in 6. Pretreatment MNC and plasma EBV-DNA were detectable in 6 and 14 patients, respectively. The maximum copy numbers were 780 copies/microgram DNA for MNC and 71000 copies/mL for plasma. Significant correlation was observed between mononuclear and plasma EBV-DNA copies (r = 0.8741, P < 0.0001). Plasma EBV-DNA well correlated with pretreatment clinical stage (P = 0.02), presence of B-symptom (P = 0.02), ECOG PS (P = 0.02), serum LDH level (P = 0.05), and soluble IL-2 receptor (P < 0.0001), but not with regional node involvement (P = 0.17), nasal vs. nasal-type (P = 0.16), and serum C-reactive protein (P = 0.29). Among 28 patients evaluable for response, 21 patients responded (CR/PR) to the first line treatment. Mean plasma EBV-DNA copy number before treatment was significantly higher in non-responders compared to responders (16472 copies/mL vs 2645 copies/mL, P = 0.02). 2-year overall survival was 69.7%. The median follow-up of patients was 2.9 years. Clinical stage, performance status, pretreatment plasma EBV-DNA and pretreatment mononuclear cell EBV-DNA were significant prognostic factors for overall survival by univariate analysis. Multivariate analysis showed clinical stage (hazard ratio = 9.0, 95% confidence interval: 1.8–45.0) and pretreatment plasma EBV-DNA (hazard ratio = 10.6, 95% confidence interval: 1.3–87.0) were significant prognostic factors. 2-year overall survival of plasma EBV-DNA positive and negative patients was 42.9% and 94.4%, respectively (Figure, P = 0.0009).
Our study shows pretreatment plasma EBV-DNA copy number is a good indicator for both response to treatment and overall survival. Measurement of the plasma EBV-DNA is useful for prospective clinical trials and general practice.
Oshimi:Eisai Pharmaceutical Company: Employment.
Asterisk with author names denotes non-ASH members.