Fractionated 9°Y-ibritumomab tiuxetan radioimmunotherapy as an initial therapy of follicular lymphoma: an international phase II study in patients requiring treatment according to GELF/BNLI criteria.

PURPOSE: We report an international, multicenter phase II trial to evaluate the efficacy and toxicity of fractionated (90)Y-ibritumomab tiuxetan ((90)Y-IT) as initial therapy of follicular lymphoma (FL). PATIENTS AND METHODS: A total of 74 patients, with a median age of 61 years (range, 28 to 80 years), were recruited requiring initial therapy by Groupe d'Etude des Lymphomes Folliculaires (GELF)/British National Lymphoma Investigation (BNLI) criteria. Among them, 78% had stage III-IV disease, 32% intermediate, and 44% high-risk (according to FL International Prognostic Index). Treatment consisted of two doses of (90)Y-IT (11.1 MBq/kg) administered 8 to 12 weeks apart. Patients with more than 20% lymphoma infiltration of bone marrow (BM) received one infusion per week for 4 consecutive weeks of rituximab (375 mg/m(2)) and proceeded to fractionated radioimmunotherapy (RIT) only if a repeat BM biopsy demonstrated clearing of lymphoma to less than 20% involvement. The primary end point was end of treatment response of the intention-to-treat population. Secondary objectives were safety and progression-free survival (PFS). RESULTS: Initial overall response rate (ORR) was 94.4% (68 of 72 patients) with combined complete response (CR/CRu) of 58.3% (42 of 72 patients). Nine patients subsequently improved response making an ORR of 95.8% (69 of 72 patients) and CR/CRu of 69.4% (50 of 72 patients). At a median follow-up of 3.1 years (range, 0.2 to 5.2 years) estimated 3-year PFS is 58%, treatment-free survival 66%, and overall survival 95%. Median PFS is 40.2 months. Thirty patients have experienced disease progression and 24 have required further treatment. The treatment was well tolerated with few (2.8%) grade 3 or 4 infectious episodes or adverse events and manageable hematologic toxicity. CONCLUSION: Fractionated RIT using (90)Y-IT is an effective initial treatment for advanced-stage FL in patients with higher tumor burden requiring treatment.