This study aims; to assess the efficacy of shortened systemic chemotherapy in patients with completely excised CD20 positive Diffuse Large B-cell Lymphoma (DLBCL) with Ann Arbor Stage I or II.

Unlike the limited stage diffuse Large B-cell Lymphoma (DLBCL) treated with primary chemotherapy followed by radiotherapy, patients with stage I or II DLBCL would be treated with surgical resection followed by chemotherapy in this trial. While chemotherapy is the main treatment modality and radiotherapy becomes adjuvant treatment in the former treatment scheme, surgical resection will remove all the gross lesions and chemotherapy aims to remove all microscopic disease whichever exists in the latter treatment scheme. Currently, six cycles of chemotherapy is usually performed after surgery even without any residual lesion compared with three cycles of chemotherapy in the former treatment scheme which plays primary role in the treatment scheme. The investigators will investigate whether abbreviated 3 cycles of Rituximab Plus Cyclophosphamide, Adriamycin, Vincristine, and Prednisolone (R-CHOP) immunochemotherapy following complete resection is an effective and safe treatment.

Inclusion Criteria:

• Patients who underwent curative resection of primary tumor
• Pathologically confirmed CD20 positive diffuse large B-cell lymphoma (DLBCL) after surgical resection
• Ann Arbor Stage I or II
• No history of chemotherapy
• Performance status: ECOG 0-2
• Age: 18 to 70 years old
• Complete excision with negative resection margin on pathologic report after surgery
• Cardiac ejection fraction ≥ 50% as measured by MUGA or 2D echocardiography without clinically significant abnormalities
• Adequate renal function: serum creatinine level below 2 mg/dL (177μmol/L)
• Adequate liver functions: Transaminase (AST/ALT) < 3X upper normal value, Bilirubin < 2X upper normal value
• Adequate hematologic function: hemoglobin ≥ 9 g/dL, absolute neutrophil count (ANC) ≥ 1,500/mm3 and platelet count ≥ 75,000/mm3
• Informed consent

Exclusion Criteria:

• Patients with a known history of HIV (+) or HCV (+). However, HBV(+) patients are eligible if primary prophylaxis is given

• Previous or concurrent cancer that is distinct in primary site or histology from DLBCL, EXCEPT cervical carcinoma in situ, treated basal cell carcinoma, superficial bladder tumors (Ta, Tis & T1). Any cancer curatively treated > 3 years prior to entry is permitted

• Pregnant or lactating women, women of childbearing potential not employing adequate contraception

• Other serious illness or medical conditions

  1. Unstable cardiac disease (i.e. congestive heart failure, arrhythmia symptomatic coronary artery disease) despite treatment, myocardial infarction within 6 months prior to study entry
  2. History of significant neurological or psychiatric disorders including dementia or seizures
  3. Active uncontrolled infection (viral, bacterial or fungal infection)
  4. Other serious medical illnesses

• Known hypersensitivity to any of the study drugs or their ingredients

• Concomitant administration of any other experimental drug under investigation, or concomitant chemotherapy, hormonal therapy, or immunotherapy

• Patient with B symptoms or Bulky disease