Inclusion Criteria:

Patients must have/be

1. Age 18 to 65 years. Patients between age 66 and 69 may be enrolled if judged to be in
excellent physical condition as per treating physician and study investigator and
based on institutional practice.

2. Diagnosis of Non-Hodgkin lymphoma, follicular, marginal zone, small lymphocytic
lymphoma, mantle cell lymphoma or transformed from an indolent NHL to aggressive
histology disease lymphoma as defined by the World Health Organization.

3. Disease relapsed after, refractory or failing to achieve a PR after two or more
cycles of intensive salvage chemotherapy (R-ESHAP or other) or disease relapsed after
autologous stem cell transplantation. Poor partial response is defined as less than
50% reduction of tumor size. Salvage chemotherapy has to be administered after either
1st, 2nd or 3rd relapse

4. Disease expressing the CD 20 antigen

5. ECOG performance status 0-2

6. Judged to be able to tolerate NST and Zevalin treatment based on institutional
criteria.

7. Signed written informed consent

8. At least one fully HLA matched sibling without evident contraindications to the
donation procedures and willing to sign consent for donation

Exclusion Criteria:

Patients must not have/be

1. Abnormal renal function (creatinine > 1.5 x upper limit of normal (ULN)

2. Abnormal hepatic function (bilirubin > 2 x ULN, ALT/AST>2x ULN)

3. Cardiac ejection fraction <40% and/or other significant cardiac compromise

4. Severe defects in pulmonary function tests or receiving continuous oxygen

5. Severe concurrent illness, such as symptomatic congestive heart failure, severe
arrhythmias, uncontrolled hypertension, diabetes, severe neurologic or psychiatric
disorder or known HIV positive

6. Previous or concurrent cancer that is distinct in primary site or histology from the
cancer being evaluated except cervical carcinoma in situ, treated basal cell
carcinoma, superficial bladder tumors (Ta, Tis & T1) that may impact on patients life
expectancy or any cancer curatively treated < 3 years prior to study entry.

7. History of prior allogeneic bone marrow transplant

8. Evidence of active hepatitis B or C infection or positivity for hepatitis-B surface
antigen

9. Known type 1 hypersensitivity or anaphylactic proteins to any component of the
Zevalin therapy or a history or presence of human anti-mouse antibodies (HAMA)

10. A female patient who is pregnant or breast feeding and an adult of reproductive
potential who is not employing an effective method of birth control during the study.

11. CNS lymphoma

12. Ongoing confirmed or suspected significant infection

13. Prior treatment with radioimmunotherapy

14. Other condition preventing participation in standard NST

15. No fully matched sibling donor