30Gy Versus 40Gy Involved-field Radiotherapy for Localized Diffuse Large B Cell Lymphoma Achieving CR After Chemotherapy

Inclusion Criteria: * biopsy-proved Diffuse Large B cell lymphoma * nonbulky stage I, nonbulky stage IE, nonbulky stage II, or nonbulky stage IIE disease(Bulky disease was defined as a mass 10 cm or more in maximal diameter) according to Ann Arbor Staging * provide written informed consent * Complete regression after chemotherapy * Considerable to CT simulation and 3D CRT or IMRT * Performance status 0-2 WHO criteria；life expectation\>6 months * negative for human immunodeficiency virus syndrome (HIV) * Minimal staging included chest radiograph, computed tomography of the abdomen and pelvis, and single percutaneous bone marrow biopsy and blood studies Exclusion Criteria: * primary mediastinal large B cell lymphoma * dermatological lymphoma * testicular lymphoma * primary central nerve system lymphoma * prior RT * history of low-grade lymphoma congestive * history of heart failure (CHF; New York Heart Association \[NYHA\] classifications III-IV), history of neoplasm (adequately treated basal cell carcinoma of the skin or in situ carcinoma of the uterine cervix were allowed), abnormal liver function tests (aminotransferases and alkaline phosphatase \> 2.5 times the upper limit of normal, bilirubin \> 50 ), renal insufficiency (serum creatinine \> 300 ), and patients with any serious medical or psychiatric illness that would prevent informed consent or completion of protocol-prescribed treatment and follow-up