PD-1 Antibody, Chidamide, Lenalidomide and Etoposide for Relapsed or Refractory NK/T Cell Lymphoma

Inclusion Criteria: 1. age:14-65 years;Eastern Cooperative Oncology Group (ECOG)score≤2;expected survival≥3 months; 2. patients with NK/T Cell Lymphoma diagnosed by immuno-histochemistry (IHC) or fluorescence in situ hybridization (FISH); 3. Refractory or relapse after at least 2 regimen; 4. Once the patient received radiotherapy, need to be more than 3 months away from this treatment, and it is a non-primary recurrence; 5. No chemotherapy contraindications: hemoglobin ≥ 100g / L, absolute neutrophil count ≥ 1.5 × 109 / L, platelets ≥ 80 × 109 / L, ALT, AST ≤ 2 times the upper limit of normal, serum total bilirubin ≤ 1.5 times normal Upper limit, serum creatinine ≥ 1.5 times normal upper limit, serum protein ≥ 30g / L; 6. At least one measurable lesion; 7. There are no other serious diseases that conflict with this program, and the cardiopulmonary function is normal; 8. Women of childbearing age must have a negative urine or blood pregnancy test, and male patients should be contraceptive during medication; 9. There is no other antitumor treatment, but bisphosphonate for anti-bone metastasis treatment and other symptomatic treatment can be applied; 10. Can understand the situation of this study and sign the informed consent voluntarily Exclusion Criteria: 1. rejecting providing blood preparation; 2. allergic to drug in this study or with hemophagocytic syndrome; 3. rejecting adopting reliable contraceptive method in pregnancy or lactation period; 4. uncontrolled internal medicine disease(including uncontrolled diabetes,severe incompetence cardiac,lung,liver and pancreas）； 5. with severe infection; 6. with primary or secondary central nervous system tumor invasion; 7. with Chemotherapy or radiotherapy contraindication; 8. ever suffered with malignant tumor; 9. Human immunodeficiency virus (HIV)-positive patients 10. Drug abuse or long-term alcohol abuse that affects the evaluation of test results; 11. Have peripheral nervous system disorder or mental disorder; 12. Patients with immune system diseases; 13. Those who have no legal capacity or whose research is affected by medical or ethical reasons;