Inclusion Criteria:

- Histologically confirmed diffuse large B cell lymphoma Elderly (>65 years) or
medically ineligible to standard cytotoxic chemotherapy due to poor performance
status, or relapsed or refractory patients Eastern Cooperative Oncology Group
performance status ≤ 2, age≥ 20 years Relapsed or refractory after autologous
hematopoietic stem cell transplantation (auto-HSCT) in young patients with good
performance status and indicated to high dose chemotherapy and auto-HSCT More than
one measurable lesion

- More than 2cm sized lesion in conventional CT scan,

- More than 1cm sized lesion in spiral CT or contrast-enhanced PET/CT Adequate renal
function (serum creatinine ≤ 2.0 mg/dl or Ccr ≥ 60 ml/min) Adequate hepatic function
(serum bilirubin ≤ 2.0 mg/dl , AST/ALT ≤ 3 upper normal limit) Adequate bone marrow
reservoir (ANC ≥1,500/㎕, platelet count≥ 75,000/㎕) patient who agree the purpose and
intention of this clinical trial

Exclusion Criteria:

- recent (<5 years) history of other malignancy or unrecovered from the disease
(appropriately treated skin cancer and uterine cervix carcinoma in situ are excluded)

- hemodynamically unstable due to the recent (<12 months) history of severe heart
disease such as myocardial infarction

- acute complications of severe lung or metabolic disease

- Combined severe neurological or psychiatric disease Unrecovered from infection
or other medical disease Recent (<30 days) history of enrollment of other
clinical trial Pregnant or breast-feeding woman women of childbearing potential
and men not employing adequate contraception at least for 1 year Previous
history drug allergy to the content of 131I-rituximab Infection(sepsis,
pneumonia, viral infection, etc) (inactivated hepatitis B carrier can be
enrolled) Young patient with good performance status indicated to autologous
hematopoietic stem cell transplantation irrespective of the failure of 1st line
chemotherapy