Pegaspargase and Methotrexate Based Regimens for Newly Diagnosed Extranodal NK/T Cell Lymphoma

Extranodal NK/T cell lymphoma is a kind of tumor more prevalent in Asia and South America than that in the Western world, which is almost invariably EBV- associated and often presents as localized disease in and around the nasal structures. The disease frequency was higher in Asian countries with no differences in age, gender or immunophenotypic profile between nasal and extranasal cases. EBV is a constant finding, particularly in the cases presenting as localized nasal disease and assumed involved in the pathogenesis. During the past decades the disease, historically termed as "lethal midline granuloma" was very aggressive with poor survival. Five-year OS for extra-nasal disease is reported as 9% compared to 42% for localized disease. Although radiotherapy combined with or without anthracycline-based chemotherapy has been considered as the treatment for extranodal NK/T cell lymphoma in the past, numerous data suggest that this tumor is not very chemosensitive due to the p-glycoprotein expression, which may mediate the drug resistance. CHOP/CHOP-like schedules presented with low CR rates and frequent failures during chemotherapy. Disseminated involvement is much poorer in prognosis than localized disease with the latter is benefit more from radiotherapy. In the nearest ten years, many new agents have been used in the treatment of extranodal NK/T cell lymphoma, in which the most promising one is asparaginase. Asparaginase-containing regiment has demonstrated about 50% responses rates and 5-year overall survival of 65% in relapsed or refractory disease. The impressive outcome indicates its value in the newly diagnosed patients, especially in the disseminated cases. Pegaspargase as a new form of asparaginase displays equivalent bioactivity as L- asparaginase with longer half-time and lower incidence of allergy. Its clinical efficacy has been verified in the patients with acute lymphocytic leukemia. The purpose of this study is to evaluate the efficacy and safety of pegaspargase and methotrexate based regimens with or without radiotherapy in the newly diagnosed patients with extranodal NK/T cell lymphoma, including localized and disseminated cases.