Inclusion Criteria:

1. Written informed consent

2. Histologically confirmed B-cell lymphoma of the following subtypes:

- LBCDL

- Grade 3b follicular lymphoma

- Mantle-cell lymphoma

- Transformed B-cell lymphoma

- Burkitt lymphoma in patients not eligible for a conventional allogeneic
transplant

3. High-risk B-cell CD20+ lymphoma defined by

- Having attained less than PR after two chemotherapy lines

- Post-transplantation relapse

- Presence of disease detected through a metabolic approach (PET/CT or else
CT+PET) either before or after autologous transplantation

- Inability to collect enough stem cells for autologous transplantation

4. Stable disease at the time of transplantation

5. Age between 18 and 65

6. Performance status (ECOG) ≤ 2

7. Normal and suitable pulmonary function (DLCO ≥ 30%)

8. Left ventricular ejection fraction (LVEF) determined by ventriculography or
echocardiogram ≥ 40%

9. Normal hepatic and renal function, with creatinine ≤ 2 mg/dl and Bi ≤ 1.5 mg/dl, and
alkaline phosphatase ≤ 2.5 x UNL ; AST, ALT ≤ 2.5 x UNL (≤ 5 x UNL if hepatic
infiltration)

Exclusion Criteria:

1. Prior treatment with radiopharmaceutical agents

2. HIV-associated lymphoma

3. Presence of human anti-mouse antibodies (HAMA) or anti-chimeric antibodies (HACA)

4. Patient's inability to follow the protocol

5. Hypersensitivity to 90Y-itritumomab tiuxetan

6. Presence of severe pathologies that preclude chemotherapeutic treatment

7. Pregnant women or pregnancy risk due to inappropriate contraceptive measures

8. Breastfeeding women