Zevalin-Containing Nonmyeloablative Conditioning for Stem Cell Transplantation (SCT)

Inclusion Criteria:

1. 18 to 70 years of age.
2. Patients with the following CD20+ lymphoid malignancies who are eligible for allogeneic transplantation: a. Relapsed or refractory follicular lymphoma; b. Relapsed or refractory or high risk mantle cell lymphoma (hi ki67; blastic); c. Recurrent or refractory marginal zone; d. Recurrent or refractory CLL/small lymphocytic lymphoma; e. Double-hit lymphoma; f. Diffuse large B cell lymphoma; g. Richter's patients; or h. Refractory or recurrent Burkitts.
3. Patients who meet criterion #2 or have any of the following are eligible: a. Less than PR to salvage chemotherapy; b. Kinetic failure; c. Having received more than 3 lines of therapy; d. Failure to mobilize autologous stem cell; e. 10% or more marrow involvement; f. 6 months post autologous stem cell transplant.
4. Patients must have a fully-matched related donor or a matched unrelated donor identified. Double cord (at least 4/6 matched) can be used if no adult matched donor is available.
5. Performance score of at least 80% by Karnofsky or 0 to 2 ECOG.
6. Left ventricular EF \>/= 45% with no uncontrolled arrythmias or symptomatic heart disease.
7. FEV1, FVC \>/= 60% and corrected DLCO \>/= 60%.
8. Serum creatinine \</=1.6 mg/dL. Serum bilirubin \< 2 mg/dL (unless due to Gilbert's Syndrome).
9. SGPT \< 2 X upper limit of normal.
10. Men and women of reproductive potential must agree to follow accepted birth control methods (i.e., a hormonal contraceptive, intra-uterine device, diaphragm with spermicide, condom with spermicide, or abstinence) for the duration of the study.
11. Negative Beta HCG test within 30 days in a woman with child bearing potential defined as not post-menopausal for 12 months or no previous surgical sterilization). Pregnancy testing is not required for post-menopausal or surgically sterilized women.

Exclusion Criteria:

1. Patient with active CNS involvement with lymphoid malignancy.
2. Known infection with HIV, HTLV-I, Hepatitis B, or Hepatitis C.
3. Patients with other malignancies diagnosed within 2 years prior to study registration. Skin squamous or basal cell carcinoma are exceptions.
4. Active bacterial, viral or fungal infections.
5. History of stroke within 6 months prior to study registration.
6. A prior allogeneic stem cell transplant.
7. Patient has received other investigational drugs within 3 weeks before study registration.
8. Presence of circulating malignant lymphoid cells or bone marrow with lymphoma that constituted more than 25% of the cellular elements.
9. Serious nonmalignant or malignant disease or psychiatric illness, which, in the opinion of the investigator would compromise protocol objectives or interfere with participation.
10. Patients who are breast-feeding.