Long-term follow up of rates of secondary malignancy and late relapse of two trials using radioimmunotherapy consolidation following induction chemotherapy for previously untreated indolent lymphoma.

Existing data suggest that myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) peak in incidence 5-10 years following exposure to ionizing radiation, while most publications report less than 5 years of follow-up after radioimmunotherapy (RIT). We report the rate of secondary MDS/AML among 60 patients treated with two front-line sequential chemotherapy-RIT trials with over 11 years of follow-up. Among 35 patients evaluated after fludarabine-RIT and 25 patients evaluated after CVP (cyclophosphamide, vincristine, prednisone)-RIT treatment, the crude, cumulative and Kaplan-Meier rates of MDS/AML at 11 years of follow-up from the combined trials were 0.12/person, 0.010/person-year and 14% (95% confidence interval [CI] 5-24%), respectively. Additionally, we found that patients treated with RIT consolidation appear to have durable remissions but that relapses after 10 years do occur. Studies of efficacy and secondary MDS/AML that report fewer than 10 years of follow-up likely underestimate risk.