To observe the efficacy and safety of Chidamide combined with prednisone, cyclophosphamide, etoposide and methotrexate in relapsed or refractory PTCL.

Prednisone, cyclophosphamide, etoposide, and methotrexate regimens are derived from a "metronidazole, etoposide, procarbazine and cyclophosphamide (PEPC) regimen" regimen that differs from the traditional "maximal Tolerance "chemotherapy, and the use of low-dose chemotherapy, frequent drug therapy, the purpose is to anti-angiogenesis and reduce drug resistance. At present, the program in our treatment of relapsed or refractory PTCL patients effective, safe and controllable, but also look forward to other joint treatment, so as to achieve better curative effect. To provide new treatment options for such patients.

Inclusion Criteria:

1. Histopathologically confirmed peripheral T-cell lymphoma (PTCL) patients;
2. Patients who have had at least one systemic treatment (including chemotherapy, hematopoietic stem cell transplantation, etc.) who have not remission or relapsed after remission;
3. For various reasons can not be hematopoietic stem cell transplantation in patients;
4. The age of 18-75 years old, male, female open;
5. ECOG (Eastern Cooperative Oncology Group) physical scoring 0-1 points;
6. Absolute value of neutrophil≥1.5 × 109 / L, platelet≥90 × 109 / L, hemoglobin≥90g / L;
7. The expected survival time ≥ 3 months;
8. No radiotherapy, chemotherapy, targeted therapy or hematopoietic stem cell transplantation were performed within 4 weeks prior to enrollment.
9. Voluntary signature of written informed consent.

Exclusion Criteria:

1. Pregnancy, breastfeeding women and unwilling to take contraceptive measures of reproductive age patients;
2. B-mode ultrasonography showed that the width of end-diastolic pericardial dark area was ≥10mm;
3. Patients receiving organ transplants;
4. Patients receiving symptomatic treatment of pre-bone marrow toxicity within 7 days prior to enrollment;
5. Patients with active bleeding;
6. Liver function abnormalities (total bilirubin> 1.5 times the upper limit of normal, ALT( alanine aminotransferase) / AST (Aspartate aminotransferase)> 2.5 times the upper limit of normal or hepatic involvement of ALT / AST> 5 times the upper limit of normal), renal dysfunction Creatinine> 1.5 times the upper limit of normal), electrolyte abnormalities;
7. Persons with mental disabilities / those who can not obtain informed consent;
8. Patients with drug abuse and long-term alcohol abuse that may affect the evaluation of test results;
9. The investigators determined that they were not fit to participate in the trial.