Extranodal NK/T-cell Lymphoma

EBV-driven NK/T-cell malignancy — nasal-type presentation, asparaginase-based chemotherapy, and poor prognosis in advanced disease

Key Points

• Extranodal NK/T-cell lymphoma (ENKTL), nasal type, is a highly aggressive EBV-associated lymphoma derived from NK cells or cytotoxic T cells, with a striking geographic predilection for East Asia and Latin America.
• The nasal/upper aerodigestive tract is the most common primary site; extranasal ENKTL (skin, GI tract, testis) carries a worse prognosis.
• EBV is uniformly detectable in tumor cells; plasma EBV DNA is a critical biomarker for diagnosis, response assessment, and surveillance.
• Asparaginase-based regimens — SMILE, DDGP, or AspaMetDex — are the cornerstone of treatment, exploiting the absence of asparagine synthetase in NK cells; anthracycline-based CHOP is largely ineffective.
• Pembrolizumab and other PD-1/PD-L1 inhibitors have demonstrated activity in relapsed/refractory ENKTL, leveraging the high PD-L1 expression driven by EBV LMP1 and copy number gains at 9p24.
• Localized (stage I–II) nasal ENKTL is treated with concurrent chemoradiotherapy (radiation ≥50 Gy) and has a 5-year OS of 60–80%; disseminated disease carries a median OS of less than 12 months.

Epidemiology and Pathogenesis

ENKTL has a distinctive geographic distribution, accounting for 5–15% of all lymphomas in East Asia (China, Korea, Japan) and Latin America, compared to less than 1% in Western countries. This epidemiology mirrors the regional seroprevalence of EBV strains with specific LMP1 deletions associated with increased oncogenicity. The tumor arises from NK cells or cytotoxic T cells (γδ or αβ). Despite their different lineages, both share a common cytotoxic phenotype (CD56+, TIA-1+, granzyme B+) and harbor latent EBV infection (latency II pattern: LMP1+, EBER+, EBNA1+, LMP2A+). EBV LMP1 drives NF-κB…

Clinical Presentation and Diagnosis

ENKTL most commonly presents in the nasal cavity and upper aerodigestive tract (Waldeyer's ring, nasopharynx, paranasal sinuses, palate). The classic presentation is a destructive midline facial lesion with nasal obstruction, epistaxis, and facial swelling — historically called "lethal midline granuloma" before the lymphomatous etiology was recognized. Bony destruction of the nasal septum, palate, or orbit may occur with advanced local disease. Extranasal ENKTL presents as primary disease in the skin, gastrointestinal tract, testis, or soft tissue without upper aerodigestive involvement, and…

Staging and Prognostic Models

ENKTL is staged using the Ann Arbor/Lugano classification. Approximately 60–70% of nasal ENKTL presents at stage I–II; extranasal ENKTL more commonly presents at stage III–IV. The Prognostic Index of NK-cell Lymphoma (PINK) incorporates age >60, stage III/IV disease, distant lymph node involvement, and non-nasal disease. The PINK-E model adds circulating EBV DNA, which is the single most powerful prognostic factor. Risk groups (PINK-E): - Low risk (0 factors): 3-year OS ~82% - Intermediate risk (1 factor): 3-year OS ~56% - High risk (≥2 factors): 3-year OS ~27% Plasma EBV DNA >6,100…

Treatment

**Localized Disease (Stage I–II, Nasal)** Concurrent chemoradiotherapy (CCRT) with radiation ≥50 Gy is the standard of care. Radiation is central given the chemoresistance of ENKTL to anthracycline-based regimens (MDR1/P-glycoprotein overexpression renders CHOP largely inactive). Asparaginase-based regimens used concurrently or sequentially with radiation include: - **DDGP** (dexamethasone, cisplatin, gemcitabine, pegaspargase): used at many Chinese centers; phase II data show excellent outcomes in localized disease - **P-GemOx** (pegaspargase, gemcitabine, oxaliplatin): active combination -…

Prognosis and Follow-up

Stage I–II nasal ENKTL treated with CCRT achieves 5-year OS of 60–80% at experienced centers. However, relapse occurs in 30–40% of patients, often at distant sites, and salvage is challenging. Stage III–IV disease has a median OS of less than 12 months with conventional therapy. HLH complicating ENKTL carries a mortality rate exceeding 50% and requires immediate intervention with high-dose dexamethasone and etoposide while initiating lymphoma-directed therapy. Post-treatment surveillance includes clinical examination, imaging (PET-CT at 3 and 6 months post-treatment), and serial EBV DNA…