Time to treatment response in patients with follicular lymphoma treated with bortezomib is longer compared with other histologic subtypes

Purpose: To determine the antitumor activity of the novel proteasome inhibitor bortezomib in patients with indolent non-Hodgkin's lymphoma. Experimental Design: Patients with follicular lymphoma (FL), marginal zone lymphoma, mantle cell lymphoma, small lymphocytic lymphoma/chronic lymphocytic leukemia, and Waldenstrom's macroglobulinemia were eligible for study. Bortezomib was given at a dose of 1.5 mg/m² as an i.v. push on days 1, 4, 8, and 11 of a 21-day cycle. Eligibility included the following: (a) no more than three prior therapies, (b) at least 1 month since prior chemotherapy, (c) measurable disease, and (d) an absolute neutrophil count of >1,000/μL and a platelet count >50,000/μL for the first dose of any cycle. Results: Seventy-seven patients were registered, of which 69 were assessable for response based on the completion of two cycles of therapy. Subtypes included FL (59.5%), mantle cell lymphoma (52%), small lymphocytic lymphoma/chronic lymphocytic leukemia (16.2%), marginal zone lymphoma (21.6%), and one Waldenstrom's macroglobulinemia. The median number of prior therapies was three. Themost common grade 3 toxicity was lymphopenia (35%) and thrombocytopenia (31%). Twenty-five patients experienced grade ≤2 sensory neuropathy (32), and 8% experienced grade 3 neurosensory toxicity. The overall response rate was 45% (40% on an intention to treat) including 10 complete remissions. Of 18 patients with FL, 9 responded with 4 complete response. The median time to treatment response for FL was 12 weeks, whereas the median time to treatment response for other subtypes of non-Hodgkin's lymphoma was only 4 weeks. Conclusions: These data suggest that bortezomib has significant single agent activity in patients with FL, and that longer durations of treatment may improve overall response.