Background: Small series suggest retreatment of indolent lymphomas with murine anti-CD20 radioimmunotherapy is effective. The longer half-life of iodine-131 ((131)I)-rituximab may result in increased bone marrow exposure, with greater toxicity on repeat administration. We examined the effects of a second (131)I-rituximab in patients with indolent lymphoma following relapse.
Patients and methods: We analyzed two institutional databases from January 2000 to July 2007 for retreatment with (131)I-rituximab. The severity of cytopenia, development of myelodysplasia (MDS), acute myeloid leukemia (AML) and hypothyroidism was noted. We compared response duration and toxicity of the treatments.
Results: Fourteen of 16 patients responded with nine complete responses (CRs), with a median duration of 10.5 months in responders. Six of 13 reresponders had the same or a longer response and six more remain in complete response. The median event-free survival was not significantly different for the two treatments. There was no significant difference in the severity of myelosuppression. Four patients developed hypothyroidism with three requiring thyroxine. One patient developed AML, with no other cases of MDS. The actuarial progression-free survival rate at 12 months was 36%.
Conclusions: Repeat (131)I-rituximab induces high response rates, some of which result in durable remissions in patients who had previously responded.