Bortezomib may be safely combined with Y-90-ibritumomab tiuxetan in patients with relapsed/refractory follicular non-Hodgkin lymphoma: a phase I trial of combined induction therapy and bortezomib consolidation.

Preclinical studies suggest that bortezomib, through inhibition of nuclear factor-kappa B (NF-kappa B) activation, may enhance the effects of radioimmunotherapy. This phase I trial was designed to determine the maximum tolerated dose (MTD) of weekly bortezomib induction combined with Y-90-ibritumomab tiuxetan followed at the time of count recovery by weekly bortezomib consolidation in patients with relapsed/refractory follicular or transformed non-Hodgkin lymphoma. Grade 3 or 4 toxicities were observed in eight of nine treated patients, and all but one of these toxicities were hematologic. One patient had grade 3 cardiotoxicity. A dose limiting toxicity (DLT) of grade 4 thrombocytopenia was observed in two of three patients treated with bortezomib at 1.6 mg/m(2), resulting in a MTD of 1.3 mg/m(2). The overall response rate was 89% (two complete response [CR], six partial response [PR], one stable disease [SD]), with a median progression-free survival of 6.5 months (range: 3-22.5 + months). A phase II trial at the MTD is under way to better define the toxicity and effectiveness of this regimen.