Y90 Ibritumomab Tiuxetan Post R-CHOP Chemotherapy for Advanced Stage Follicular Lymphoma

Inclusion Criteria:

* Age greater than or equal to 18 years.
* Biopsy demonstration of a CD20+ follicular non-Hodgkin's lymphoma diagnosed according to the World Health Organization (WHO) classification (grade I, II, or IIIa).
* Staging demonstration of advanced stage disease (stage III or IV) according to the Ann Arbor staging system.
* Intermediate or high-risk prognostic score (2-5 points) according to the follicular lymphoma international prognostic index (FLIPI).
* Adequate performance status (less than or equal to 2) according to the Eastern Cooperative Oncology Group (ECOG) (Zubrod) scale.
* No prior radiotherapy or systemic therapy, including chemotherapy or immunotherapy (rituximab).
* Bi-dimensional measurable disease by physical examination or radiographic evaluation (disease measurements at least 1.5 cm x 1.5 cm) or assessable disease on bone marrow evaluation.
* Clinical criteria for therapeutic intervention, as previously reported by Hiddeman, including one of: the presence of B-symptoms, bulky disease (mediastinal lymphomas \>7.5 cm or other lymphomas \>5 cm in maximal diameter), an impairment of normal hematopoesis with hemoglobin \<10g/mm3, granulocytes \<1500/mm3, or platelets \<100,000/mm3, and/or a rapidly progressive disorder.
* Patient consent must be obtained according to the Sunnybrook Health Sciences Centre Research Ethics Board requirements. A sample consent form is given in Appendix I. The patient must sign the consent form prior to registration.
* Patients must be accessible for treatment and follow up. Patients registered on this trial must complete their therapy with 90Y Ibritumomab Tiuxetan at the participating centre. Induction chemotherapy with R-CHOP should also be completed at the participating centre, but exceptions can be made according to the discretion of the centre's primary investigator.
* Protocol treatment is to begin within 5 working days of patient registration

Exclusion Criteria:

* Pregnancy or women who intend to breast-feed during the study period.
* Follicular non-Hodgkin's lymphoma grade IIIb histology, according to the World Health Organization (WHO) classification.
* Known human immunodeficiency virus infection or hepatitis B viral infection.
* Life expectancy less than or equal to 3 months, according to physician judgement.
* Evidence of left ventricular (LV) dysfunction (ejection fraction less than or equal to 50%). Demonstration of LV function is required in patients over the age of 60 or in patients with a prior history of hypertension, congestive heart failure, peripheral vascular disease, cerebrovascular disease, coronary artery disease, or cardiac arrhythmia.
* Serum creatinine, alkaline phosphatase, or total bilirubin \>2.5 times the upper limit of the normal value, unless clearly related to lymphoma.
* Concurrent uncontrolled medical disease, including severe congestive heart failure, myocardial infarction within 6 months prior to enrollment, severe chronic renal failure, or active infection, with the severity of disease judged according to the discretion of the treating physician.
* Patients with a history of other malignancies, except: (1) adequately treated non-melanoma skin cancer, curatively treated in-situ cancer of the cervix, or (2) other solid tumours curatively treated with no evidence of disease for \> 5 years