Extranodal natural killer/T-cell lymphoma (ENKTL) is an aggressive form of non-Hodgkin's lymphoma and shows extremely poor survival. This prospective pilot study to evaluate the efficacy and safety of pegylated aspargase(PEG-ASP)combined with etoposide and gemcitabine (PEG) treatment in this population.

Treatment PEG dosages were as follows: days 1 and 8,30min intravenous infusion of 1000mg/m2 gemcitabine;day1,4h intravenous infusion of 100mg/m2 etoposide,day1-3,deep intramuscular injection of 2500unit/m2 PEG-ASP at three different sites.The regimen was repeated every 3 weeks.Stage IE/IIE patients underwent four cycles induction chemotherapy, followed by involved-field radiotherapy after got complete remission ,partial regression or stable disease.Three-dimensional conformal radiotherapy was done by linear accelerator at 2.0 grays (Gy) per daily fraction with 5-6 weeks. The involved-field radiation (IFRT) dose was 50-56 Gy.Stage IIIE/IVE patients were given for a maximum of six cycles.Refractory/relapsed patients underwent at least two cycles treatments unless there was disease progression or unacceptable side effects, or withdrawal of patient consent. Autologous haematopoietic stem cell transplantation (AHSCT) was recommended after achieving CR for advanced stage and refractory/relapsed patients

Inclusion Criteria:

1. pathologically confirmed, previously untreated or refractory/relapsed ENKTL as defined by the World Health Organization classification;
2. age≥18 years;
3. Eastern Cooperative Oncology Group (ECOG) performance status of 0-2;
4. at least one measurable lesion;
5. adequate haematologic function (haemoglobin > 9.0 g/l, absolute neutrophil count > 1500/ml, platelets > 75,000/l),
6. adequate hepatic function (total serum bilirubin ≤ 1.5 times the upper limit of normal, alanine aminotransferase and aspartate aminotransferase ≤ 2.5 times the upper limit of normal),
7. adequate renal function (serum creatinine ≤ 1.5 mg/dl, creatinine clearance ≥ 50 ml/min);
8. normal coagulation function and electrocardiogram results.
9. Prior chemotherapy and radiotherapy should have been completed >4 weeks 10.earlier,willingness to provide written informed consent.

Exclusion Criteria:

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