Rituximab Maintenance Therapy for Marginal Zone B-cell Lymphoma (MZL)

Inclusion Criteria: * Histologically confirmed CD20 positive marginal zone B-cell lymphomas * Ann Arbor stage III or IV * No prior chemotherapy or radiotherapy for advanced stage MZL * Tumor response after 8th cycles of R-CVP CTx ≥ SD (Stable disease) * Performance status (ECOG) ≤ 2 * age ≥ 20 * At least one or more bidimensionally measurable lesion(s): ≥ 2 cm by conventional CT/ ≥ 1 cm by spiral CT/ skin lesion (photographs should be taken) ≥ 2 cm/ measurable lesion by physical examination ≥ 2 cm * Adequate renal function: serum creatinine level \< 2 mg/dL (177 μmol/L) * Adequate liver functions: Transaminase (AST/ALT) \< 3 X upper normal value / Bilirubin \< 1.5 X upper normal value /Alkaline phosphatase \< 5 X upper normal value * Adequate BM functions:ANC \> 1500/uL and platelet \> 75,000/uL and Hemoglobin \> 9.0 g/dL unless abnormalities are due to bone marrow involvement by lymphoma * Informed consent Exclusion Criteria: * Other subtypes NHL than MZL * Large cell component \>10% * Tumor response after 8th cycles CTx = PD (Progression disease) * Central nervous system (CNS) metastasis * Any other malignancies within the past 5 years except curatively treated non-melanoma skin cancer or in situ carcinoma of cervix uteri * Pregnant or lactating women, women of childbearing potential not employing adequate contraception * Other serious illness or medical conditions i. Unstable cardiac disease despite treatment, myocardial infarction within 6 months prior to study entry ii. History of significant neurologic or psychiatric disorders including dementia or seizures iii. Active uncontrolled infection (viral, bacterial or fungal infection) iv. Other serious medical illnesses * Known hypersensitivity to any of the study drugs or its ingredients (i.e., hypersensitivity to Polysorbate 20, CHO cell products, or recombinant human antibodies) * Concomitant administration of any other experimental drug under investigation, or concomitant chemotherapy, hormonal therapy, or immunotherapy.