RESUMEN
Lenalidomide is manageable and effective in multiple myeloma, particularly in elderly patients. Surprisingly, the combination of lenalidomide with rituximab produced clinically significant anemia at 25 mg/day for 21/28 days, the highest possible dose, in Waldenström's Macroglobulinemia (WM). We aimed to determine the maximum tolerated dose (MTD) of single agent lenalidomide and determine its impact on WM. RV-WM-0426 is a multicenter dose escalation open label phase 1/2 study of lenalidomide in relapsed/refractory WM (RRWM). Lenalidomide was given orally 21/28 days per cycle for 1 year, at escalated dose of 15 to 20 mg during phase 1 to determine the MTD; the phase 2 part was conducted at the MTD. Seventeen RRWM patients were included. The MTD was established at 15 mg/day 21/28. By ITT analysis, the overall response rate was 29%. With a median follow-up of 36 months, median TTP was 16 months (95% CI 5.5-26), the 5-year OS was 91%. The most frequent adverse events ≥ grade 3 at 15 mg were 14% anemia and 43% neutropenia. The MTD of lenalidomide is 15 mg/day 21/28 days in RRWM. Lenalidomide is active in the treatment of RRWM and the safety profile appears manageable. Future studies may look into combinations of lenalidomide and continuous dosing.