Chidamide With PET Regimen for Angioimmunoblastic T Cell Lymphoma (PET: Prednisone, Etoposide and Thalidomide)

Inclusion Criteria: 1. Pathologically diagnosed as angioimmunoblastic T cell lymphoma (diagnosed by pathologic department in IIIA hospitals or verified by certified institutions), immunohistochemistry should include: CD3, CD4, CD8, CD20, CD10, CD21, CD35, Bcl6, CXCL13, EBER, PD-1, Ki67. 2. At least on measurable focus (≥1.0\*1.0cm by imaging), or at least one evaluable focus; 3. Age 18-75 years, both male and female; 4. ECOG 0-2, KPS≥ 70points; 5. Expected survival ≥3 months; 6. Peripheral blood neutrophil count ≥1.5×10\^9/L, platelet count≥ 75×10\^9/L, Hb≥ 90g/L; 7. Liver function: bilirubin ≤1.5 times of the normal maximum; AST、ALT≤2 times of the normal maximum (for patients with liver infiltration AST、ALT≤3 times of the normal maximum); renal function: blood creatinine ≤2 times the normal maximum; 8. Negative random pregnancy test for fertile women patients within 7 days before enrollment; 9. No radiation therapy, chemotherapy, targeted therapy nor hemopoietic stem cell transplantation within 4 weeks before enrollment; 10. No anti-tumor therapy at enrollment, including herbal therapy, immunotherapy and biologic therapy, symptomatic treatment is not within this range; Exclusion Criteria: 1. Women during pregnancy or lactation, and fertile women that are not willing to take contraceptive measurements; 2. Patients with other malignant tumors simultaneously that have not been effectively controlled; 3. Patients with history of using HDAC inhibitors; 4. Patients who are allergic to medicine used in the trial, or have metabolic disorders toward these medicine; 5. Patients with severe active infection; 6. Patients with HIV or syphilis infection; 7. Patients with prolonged QT interval (male \> 450ms，female \> 470ms), or chronic heart failure patients with level III or IV cardiac function; or those have the following heart disease within 6 months before enrollment: acute coronary syndrome, acute heart failure (heart function level III or IV), distinctive ventricular arrhythmias (prolonged ventricular tachycardia, ventricular fibrillation, etc); 8. Patients with history of organ transplantation; 9. Patients with history of thrombosis and embolism; 10. Patients with mental disorders or those who are unable to sign a written consent; 11. Patients with drug abuse or long-time alcoholism that may influence the result of the trial; 12. Patients who do not have capacity of legal transactions; 13. Patients currently in other clinical trials; 14. Those who are recognized as inappropriate for the trial by the investigators;