Phase II Study of Yttrium 90 (90Y) Ibritumomab Tiuxetan (Zevalin®) in Patients with Relapsed and Refractory Mantle Cell Lymphoma (MCL).

Background: Mantle cell lymphoma (MCL) has poor clinical outcome and is a significant therapeutic challenge in patients with relapsed or refractory disease due to its resistance to salvage chemotherapy. Although recent studies have shown the clinical utility of radioimmunotherapy (RIT) in relapsed and transformed indolent B-cell lymphoma, the clinical efficacy of this treatment modality in patients with MCL is not well described. We report the results of a completed phase II clinical trial of yttrium 90 ibritumomab tiuxetan (Zevalin) in patients with relapsed and refractory MCL.

Patients and Methods: Patients with relapsed or refractory MCL with measurable disease, age ≥18 years, and performance status <3 were eligible. Patients were required to have adequate function of the bone marrow (ANC ≥1,500/mm3, platelets ≥100,000/mm3), liver, and kidneys. Patients were excluded if they had prior stem cell transplantation, RIT, CNS lymphoma, HIV infection, pleural effusion, HAMA reactivity, or circulating lymphoma cell count ≥5,000/mm3. Patients with pretreatment platelet counts ≥150,000/mm3 received a dose of Zevalin at 0.4 mCi 90Y/kg (maximum dose 32 mCi), whereas those with platelet counts <150,000/mm3 received 0.3 mCi 90Y/kg.

Results: Thirty-five patients were enrolled at MDACC. The median age was 68 years (range 52–79), and 27 patients were men. All patients had an ECOG performance status of 0 or 1 and had been previously treated with rituximab with or without other chemotherapy. The median number of prior regimens was 3 (range 1–6). Twelve of the patients did not respond to their last regimen. Twenty-two patients were previously treated with Hyper-CVAD alternating with MTX/Ara-C, and 7 previously received bortezomib. Thirty-one of 35 patients are eligible for evaluation of treatment response and toxicity. There were no grade 3 or 4 non-hematologic toxic events. Grade 1 non-hematologic toxic events included fatigue in 7 and nausea in 3. Grade 2 non-hematologic toxic events included non-neutropenic fever in 1 and melana in 1. Grade 3 or 4 hematologic toxic events included thrombocytopenia in 8, neutropenia in 2 and anemia in 1. Objective responses were observed in 13/31 patients for an overall response rate (ORR) of 42% including 8 CR/CRu’s (26%) and 5 PR’s (16%). Three patients had stable disease. Among the 4 patients who received a Zevalin dose of 0.3 mCi 90Y/kg, 1 achieved a CRu while the 3 others had progressive disease. Eight of the 13 responding patients were previously treated with 3 or more regimens; two patients achieved CR after having received 4 prior lines of therapy. Median progression free survival for the responded patients was 6 months after a median follow up time of 16 months.

Conclusion: Zevalin treatment was generally well tolerated; with the most common toxicity being hematological. The observed responses to Zevalin in heavily pretreated patients with MCL are promising and warrant further investigation of its activity after first or second relapse, and in conjunction with front-line therapy.