Phase II study on the feasibility and efficacy of consolidation with 90Y-ibritumomab tiuxetan in patients with relapsed or refractory aggressive B-cell non-Hodgkin’s lymphoma having achieved partial or complete remission after induction with R-PECC chemotherapy.

1. Histologically confirmed aggressive B-cell NHL according to the World Health Organization (WHO) classification: Follicular lymphoma grade 3b or Diffuse large B-cell lymphoma

2. Refractory disease or histologically confirmed first or second relapse(Refractory is defined as no response or partial remission according to CT. Patients in partial response (PR) can only be included in case of positive PET scan or positive biopsy)

3. CD20 positive (assessed at 1st diagnosis or from fresh histology at confirmation of relapse or immunophenotyping of circulating CD20-positive NHL cells from peripheral blood)

4. Current measurable disease, i.e. measurable in two perpendicular dimensions on physical examination or computerized tomography (CT) scan using standardized response criteria for NHL (Cheson et al, 1999)

5. Age > 18 years

6. WHO performance status 0, 1 or 2

7. Life expectancy of at least 3 months

8. Absolute neutrophil count > 1.5 x 109/l and platelet count > 100 x 109/l (unless caused by NHL infiltration in the bone marrow)

9. Written informed consent

1. Prior allogeneic stem cell transplantation-

2. Prior radioimmunotherapy

3. Patients who have received chemotherapy or radiotherapy within 6 weeks prior to study entry or who have not recovered from toxicities related to prior therapies

4. Eligibility for ASCT- ASCT within 12 months of study entry

5. Investigational drugs within 4 weeks prior to entry on this study or persistent toxic side effects of such therapy

6. Treatment with external-beam radiation therapy to more than 25% of active bone marrow

7. A history of intolerance to rituximab

8. Severe cardiac, pulmonary, neurological, psychiatric or metabolic disease which could compromise participation in the study, or serious underlying medical conditions which could impair the ability of the patient to participate in the trial

9. Hepatic dysfunction, bilirubin or transaminases >= 2.5 x upper normal limit (unless caused by the NHL)

10. Renal dysfunction, serum creatinine >=180 mmol/l or clearance <= 40 ml/min (unless caused by the NHL)

11. Active uncontrolled infections

12. Patients known to be HIV-positive

13. Current or chronic hepatitis B or hepatitis C infection

14. Symptomatic NHL localization in the central nervous system (CNS). Lumbal puncture is not required unless CNS involvement with NHL is clinically suspected

15. Transformed indolent lymphoma

16. Post-transplant lymphoproliferative disorder

17. Pregnant or breast-feeding female patients. Negative serum pregnancy test at study is mandatory for female patients of childbearing potential