Extranodal Natural Killer/T-cell Lymphoma, Nasal Type: Diagnosis and Treatment

Abstract

The aggressive lymphoma, extranodal natural killer/T-cell lymphoma-nasal type, is strongly associated with Epstein-Barr virus (EBV) and is most common in Asia and in South and Central America. By contrast, incidence is low in the United States and Europe, where extranodal natural killer/T-cell lymphoma represents only 0.2%-0.4% of all newly diagnosed non-Hodgkin lymphomas. At diagnosis, it is important to test for EBV DNA in plasma by polymerase chain reaction and to carry out positron emission tomography/computer tomography and magnetic resonance imaging of the nasopharynx. In stage I/II disease, radiotherapy is the most important treatment modality, but in high-risk stage I/II disease (stage II, age > 60 y, elevated lactate dehydrogenase, Eastern Cooperative Oncology Group performance score ≥2, primary tumor invasion), it should be combined with chemotherapy. The most optimal responses are reached with nonmultidrug resistance-based therapy (eg, asparaginase- or platinum-based therapy). Therapeutic approaches consist of either platinum-based concurrent chemoradiotherapy or sequential chemoradiotherapy. The minimum dose of radiotherapy should be 50-56 Gy. Treatment of stage III/IV disease consists of 3 cycles of chemotherapy followed by autologous hematopoietic cell transplantation. Allogeneic hematopoietic cell transplantation should only be considered in case of relapsed disease or after difficulty reaching complete remission. During treatment and follow-up, plasma EBV levels should be monitored as a marker of tumor load.

Figure 1.

Histology of an NK/T-cell lymphoma showing *extensive lymphocytic infiltration, **necrosis, and ***angiocentric growth. NK = natural killer.

Figure 2.

Proposed treatment algorithm. DeVIC = dexamethasone, etoposide, ifosfamide, and carboplatin; GELOX = gemcitabine, oxaliplatin, and L-asparaginase; HCT = hematopoietic cell transplantation; SMILE = dexamethasone, methotrexate, ifosfamide, L-asparaginase, and etoposide; VIDL = etoposide, ifosfamide, dexamethasone, and L-asparaginase.

Figure 3.

Mechanism of action of asparaginase. The lack of asparagine synthetase in NK/T-cells means that they are dependent on exogenous asparagine and glutamine. By degrading asparagine and glutamine to aspartic acid and glutamic acid, asparaginase inhibits essential intracellular protein synthesis and triggers cell death. NK = natural killer.

Figure 4.

Summary of possible new therapeutic strategies with mechanisms of action. Antibody drugs target proteins on the cellular membrane and include brentuximab-vedotin (directed against CD30) and daratumumab (directed against CD38). Anti-PD-1 antibodies (pembrolizumab, nivolumab) target microenvironmental T-cells that become inactivated when bound to PD-L1 expressed on a lymphoma. LMP1 is a transmembrane protein produced by EBV that activates the NF-kB pathway and leads to proliferation and lymphomagenesis. This, in turn, upregulates PD-L1. Other possible targets are CAR-T or BiTE directed against LMP1 or CD276 (B7-H3). BiTE = bispecific antigen engager; CAR-T = chimeric antigen receptor T-cells; EBV = Epstein-Barr virus; LMP1 = latent membrane protein 1; NF-kB = nuclear factor kappa B; PD-1 = programmed cell death protein 1; PD-L1 = programmed death-ligand 1.