330 SAFETY AND EFFICACY OF RETREATING FOLLICULAR NON-HODGKIN'S LYMPHOMA WITH 90Y IBRITUMOMAB TIUXETAN (ZEVALIN).

Background There are no data regarding safety and efficacy of treating follicular non-Hodgkin9s lymphoma (NHL) patients with a second course of Zevalin. Methods Patients with follicular NHL who received two courses of Zevalin therapy were identified nationally, and data were retrospectively collected. Results Ten patients (mean age 62.5 years, 48-91) were identified. Prior to the first Zevalin, all patients received chemotherapy (mean 2.4 courses, 1-5), 3 of 10 auto-PBSCT, and 4 of 10 external beam radiotherapy (ebRT). After the initial course of treatment, the mean time to nadir for the anemia was 7.9 weeks (4-13), neutropenia was 6.7 weeks (4-10), and thrombocytopenia was 5.2 weeks (4-8). One patient required growth factor support and transfusions; two had an incomplete recovery of platelet count at 23 and 30 weeks (76,000 and 126,000/μL). Hematologic toxicity and grades are in the table below. Prior to the second course of Zevalin two patients received ebRT, one received 131I tositumomab, and three received chemotherapy (1-5 regimens). The median time to the second Zevalin course was 613 days (183-1,300). After the second course of Zevalin, the mean time to nadir for the anemia was 8.2 wks (2-25); neutropenia was 6.7 weeks (4-10); and thrombocytopenia was 5.5 weeks (4-7). Four of 10 patients required growth factor support, 2 required transfusions, 3 had incomplete recovery of platelet count and early progression, and 2 had a maximum recovery of their platelet count at 29 and 40 weeks (143,000 and 144,000/μL). There were no infectious or bleeding complications with either course of Zevalin. No secondary myelodysplastic syndrome or acute leukemia was reported. Conclusions Retreating patients with follicular NHL with a second course of Zevalin is tolerable, with substantial evidence of clinical efficacy.