Inclusion Criteria

- Documentation of Disease

- Previously treated, histologically confirmed follicle center cell lymphoma,
World Health Organization (WHO) classification, grade 1, 2, or 3a

- Institutional flow cytometry or immunohistochemistry must confirm Cluster of
Differentiation 20 (CD20) antigen expression.

- Prior Treatment

- Patient must have been treated with rituximab either alone or in combination
with chemotherapy.

- Patient must have a time to progression of ≥ 6 months from last rituximab dose.

- No corticosteroids within two weeks prior to study, except for maintenance
therapy for a non-malignant disease. Maintenance therapy dose may not exceed 20
mg/day prednisone or equivalent.

- No prior radioimmunotherapy within 12 months of study entry.

- Age ≥ 18 years.

- Eastern Cooperative Oncology Group (ECOG) Performance Status 0-2.

- Measurable disease must be present either on physical examination or imaging studies.
Non-measurable disease alone is not acceptable. Any tumor mass >1 cm is
acceptable.Lesions that are considered non-measurable include the following:

- Bone lesions

- Ascites

- Pleural/pericardial effusion

- Lymphangitis cutis/pulmonis

- Bone marrow

- No known Central Nervous System (CNS) involvement by lymphoma.

- No known Human Immunodeficiency Virus (HIV) infection.

- Non-pregnant and non-nursing.

- Patients with a "currently active" second malignancy, other than non-melanoma skin
cancers, are not eligible.

- Patients with a recent history (within 3 months of study entry) of Deep Vein
Thrombosis/Pulmonary Embolism (DVT/PE) are not eligible.

- Required Initial Laboratory Values:

- Absolute Neutrophil Count (ANC) ≥ 1000/µL

- Platelet count ≥ 75,000/µL

- Creatinine < 1.5 x Upper Limit of Normal (ULN) unless attributed to lymphoma or
calculated clearance > 50 mL/min (patients on dialysis are not eligible)

- Total Bilirubin ≤ 2 x ULN unless attributed to lymphoma or Gilbert's disease