Melphalan, prednisone, and lenalidomide for newly diagnosed myeloma: Kinetics of neutropenia and thrombocytopenia and time-to-event results

Background: Initial analysis of the combination melphalan, prednisone, plus lenalidomide (MPR) showed significant antimyeloma activity in patients with untreated multiple myeloma, with neutropenia and thrombocytopenia as the most frequent side effects. This updated analysis reassessed the kinetics of neutropenia and thrombocytopenia as well as the safety and efficacy of MPR. Patients and Methods: A total of 21 patients with newly diagnosed myeloma received melphalan 0.18 mg/kg on days 1-4, prednisone 2 mg/kg on days 1-4, and lenalidomide 10 mg daily on days 1-21 for nine 28-day cycles, followed by maintenance therapy with lenalidomide 10 mg daily on days 1-21. Results: Grade 3/4 neutropenia occurred in 52% of the patients, and granulocyte colonystimulating factor was administered in 43%. The mean neutrophil counts at the start of each MPR cycle, during nadir, and after 6 months of maintenance were 2.69 × 10⁹/L, 1.43 × 10⁹/L, and 2.11 × 10⁹/L, respectively. Grade 3/4 thrombocytopenia occurred in 24% of the patients. Platelet transfusions were required by 1 patient (5%) with a platelet count of 16 × 10⁹/L; however, no thrombocytopenia-associated bleeding was reported. The mean platelet counts at the start of each cycle, during nadir, and after 6 months of maintenance were 174 × 10⁹/L, 121 × 10⁹/L, and 158 × 10⁹/L, respectively. Median follow-up was 29.6 months, median progression-free survival was 28.5 months, and 2-year overall survival was 91%. Conclusion: MPR is a promising regimen with manageable hematologic toxicity.