Fludarabine and Rituximab for the Treatment of Marginal Zone Non-Hodgkin's Lymphoma

Inclusion Criteria: * Histologically confirmed, newly diagnosed or relapsed MALT, marginal zone lymphoma, or low-grade B cell lymphoproliferative disorder which is CD5-, CD10- and CD20+ * Pathology must be reviewed at Brigham \& Women's Hospital, Massachusetts General Hospital, or the University of Rochester James P. Wilmot Cancer Center prior to enrollment * Documentation of CD20+ status * Must not be a candidate for local radiotherapy with curative intent * If gastric MALT, not a candidate for antibiotic therapy with curative intent * Patients with leukemic phase marginal zone lymphoma are eligible if their absolute lymphocyte count is \>10,000 / µl * Prior treatment with rituximab is permitted, if rituximab induced an objective response which persisted for at least 6 months * Prior radiotherapy is acceptable * Measurable disease * ANC: \> 1000/mm3 * Platelets: \> 100,000/mm3 * Hemoglobin: \> 7 gm/dL * Adequate renal function as indicated by serum creatinine \<= 2 mg/dL. * Adequate liver function, as indicated by serum total bilirubin \<= 2 mg/dL. * AST or ALT \<3x Upper Limit of Normal unless related to primary disease. * Men and women of reproductive potential must agree to use an acceptable method of birth control during study treatment and for six months after completion of study treatment. * WHO Performance status \</= 2 * Subject has provided written informed consent. Exclusion Criteria: * Patients with Waldenstrom's Macroglobulinemia or lymphoplasmacytic lymphoma are excluded * History of HIV * Active infection * Known CNS disease * Pregnant (a negative serum pregnancy test should be performed for all women of childbearing potential within 7 days of treatment) or currently lactating women * Prior treatment within the last three weeks * Prior fludarabine * Positive direct antiglobulin test