Radioimmunotherapy with 90-yttrium-ibritumomab tiuxetan (90Y-IT) as first-line treatment in patients with
follicular lymphoma (FL) demonstrated promising results with a complete remission (CR) rate of 56% and a median progression-free survival (PFS) of 26 months, when initially analyzed after a median follow-up of 30.6 months. The aim of this long-term follow-up was to investigate whether clinical benefits were maintained and new safety signals appeared. Fifty-nine patients, aged ≥ 50 years, with FL grade 1 to 3A in stages II to IV were treated with 90Y-IT as first-line
therapy. If CR without evidence of
minimal residual disease (MRD), partial response or stable disease was achieved 6 months
after treatment, patients were observed without further treatment. Patients with CR but persisting MRD received consolidation
therapy with
rituximab. The primary endpoint was the clinical response rate. Secondary endpoints were time to progression, safety, and tolerability. After a median follow-up of 9.6 years, median PFS was 3.6 years, and 8-year PFS was 38.3%. Median overall survival (OS) was not reached during the extended follow-up, and 8-year OS amounted to 69.2%. Age 65 years and above or
disease progression within 24 months of treatment were significantly associated with shorter OS. An important finding was the lack of new safety signals. In particular, no increase in secondary
malignancies or transformation into aggressive
lymphoma was observed compared to trials with a similar follow-up. In summary, 90Y-IT as first-line treatment demonstrates a favorable safety profile and long-term clinical activity in a substantial fraction of FL patients in need of
therapy. ClinicalTrials.gov Identifier: NCT00772655.