Follicular lymphoma (FL) and mantle cell lymphoma (MCL) are rare lymphomas which consist of less than 5% of non-Hodgkin lymphoma in Korea. Although FL with histologic grade 1 or 2 has relatively good prognosis, continual treatment is needed due to frequent relapse. FL with histologic grade 3 has poor prognosis similar to that of diffuse large B cell lymphoma. Meanwhile, the response rate to systemic chemotherapy in MCL is low, so the treatment of relapsed MCL is challenging. So we investigate the efficacy of radioimmunotherapy using 131I-rituximab in refractory or relapsed patients with FL or MCL

Inclusion Criteria:

• Histologically confirmed follicular lymphoma or mantle cell lymphoma
• relapsed or refractory patients
• Eastern Cooperative Oncology Group performance status ≤ 2
• age≥ 20 years
• 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)