High activity ⁹⁰Y‐ibritumomab tiuxetan (Zevalin®) with peripheral blood progenitor cells support in patients with refractory/resistant B‐cell non‐Hodgkin lymphomas

Radioimmunotherapy (RIT) is an alternative approach in the treatment of resistant/refractory B-cell non-Hodgkin lymphoma (NHL). We performed a feasibility and toxicity pilot study of escalating activity of 90Y-ibritumomab tiuxetan followed by autologous stem cell transplantation (ASCT). Three activity levels were fixed--30 MBq/kg (0.8 mCi/kg), 45 MBq/kg (1.2 mCi/kg) and 56 MBq/kg (1.5 mCi/kg)--and 13 patients enrolled. One week before treatment all patients underwent dosimetry. ASCT was performed 13 d after Zevalin administration. Treatment was well tolerated and all patients engrafted promptly. No differences in terms of haematological toxicities were observed among the three levels, apart from a delayed platelet recovery in heavily pretreated patients receiving 56 MBq/kg. Non-haematologic toxicity was mainly related to infections and liver toxicity. One patient died 4 months after treatment because of hepatitis C virus reactivation. One patient developed a myelodysplastic syndrome 2 years after treatment. In conclusion, high-activity Zevalin with ASCT is feasible and could be safely delivered in elderly and heavily pretreated NHL patients, including those who previously received high-dose chemotherapy and ASCT. Maximum tolerated dose was not clearly defined according to dosimetry and clinical toxicities, and further studies are needed to confirm the toxicity profile and evaluate efficacy.