Radioimmunotherapy

Radioimmunotherapy (RIT) is an attractive therapeutic option for patients with NHL, as these are radiosensitive tumors. The two clinically available radioim-munoconjugates are iodine 131I tositumomab (Bexxar) and ibritumomab tiuxetan (Zevalin) using yttrium-90. These have been used extensively in patients with indolent lymphoma, but little experience is available in MCL.

In a study from Seattle, Gopal and colleagues examined the role of 131 I-radiolabeled (Tositumomab) in relapsed MCL.79 The antibody dose was 1.7 mg/kg body weight, and the normal amount of 131 I was calculated to deliver 20-25 Gy to vital normal organs. The treatment was followed 10 days later by administration of high-dose etoposide (30-60 mg/kg), cyclophosphamide (60-100 mg/kg), and infusion of cryopreserved autolo-gous stem cells. A total of 16 patients were treated with a median number of 3 prior therapies and 7 with chemotherapy resistant disease. In 11 patients with measurable disease the CR and OS were 91% and 100%, respectively. Fifteen patients were alive at the time of evaluation and 12 had no progression of lymphoma at 6-57 months from transplant and 16-97 months from diagnosis. The ORR at 3 years from transplant was estimated at 93% and PFS at 61%. These results are encouraging and warrant further investigation.

The role of RIT in the upfront management of MCL is also being assessed. In an ongoing trial, the Eastern Cooperative Oncology Group is evaluating radioimmunotherapy after R-CHOP induction chemotherapy. While R-CHOP may be an effective induction regimen for MCL, it is not sufficient for durable remission. In this trial, patients who respond to R-CHOP are treated with 90Yttrium-ibritumomab (Zevalin).

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