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Lenalidomide and Rituximab in Waldenstrom's Macroglobulinemia

Authors' Affiliations: ¹ Bing Center for Waldenstrom's Macroglobulinemia and ² Jerome Lipper Multiple Myeloma Center, Dana-Farber Cancer Institute; ³ Harvard Medical School, Boston, Massachusetts; ⁴ Florida Cancer Specialists, Sarasota, Florida; ⁵ Commonwealth Hematology Oncology, Quincy, Massachusetts; ⁶ Pacific Hematology Oncology Associates, San Francisco, California; ⁷ University of Vermont Cancer Center, Burlington, Vermont; ⁸ Edward Hospital and Health Services Cancer Center, Naperville, Illinois; ⁹ Sanford R. Nalitt Institute for Cancer and Related Blood Disease, Staten Island, New York; ¹⁰ Hematology Oncology Associates of Western Suffolk PC, Bayshore, New York; ¹¹ Harold Alfond Center for Cancer Care, Augusta, Maine; and ¹² Monmouth Medical Center', Long Branch, New Jersey

Requests for reprints: Steven P. Treon, Bing Center for Waldenstrom's Macroglobulinemia, Dana-Farber Cancer Institute, M547, 44 Binney Street, Boston, MA 02115. Phone: 617-632-2681; Fax: 617-632-4862; E-mail: steven_treon{at}dfci.harvard.edu.

Purpose: Thalidomide and its more potent immunomodulatory derivative lenalidomide enhance rituximab-mediated antibody-dependent cell-mediated cytotoxicity. We therefore evaluated lenalidomide and rituximab in symptomatic Waldenstrom's macroglobulinemia (WM) patients naive to either agent.

Experimental Design: Intended therapy consisted of 48 weeks of lenalidomide (25 mg/d for 3 weeks and then 1 week off) along with rituximab (375 mg/m²/wk) dosed on weeks 2 to 5 and 13 to 16. Sixteen patients were enrolled, 12 of whom were previously untreated.

Results: Unexpectedly, we observed an acute decrease in hematocrit in 13 of 16 patients (median hematocrit decrease, 4.8%), which was attributable to lenalidomide patients and which led to cessation of further enrollment on this study. Lenalidomide-related anemia was observed even at doses as low as 5 mg/d and occurred in the absence of hemolysis or other cytopenias. The overall response and major response (<50% decrease in serum IgM) rates were 50% and 25%, respectively, on an intent-to-treat basis. With a median follow-up of 31.3 months, 4 of 8 responding patients have progressed with a median time to progression of 18.9 months.

Conclusion: Lenalidomide produces unexpected but clinically significant acute anemia in patients with WM. In comparison with our previous study with thalidomide and rituximab in an analogous patient population, the responses achieved in WM patients with lenalidomide and rituximab appear less favorable.