Report of phase I and II trials of melphalan, prednisolone, and thalidomide triplet combination therapy versus melphalan and prednisolone doublet combination therapy in Japanese patients with newly diagnosed multiple myeloma ineligible for autologous stem cell transplantation.

We conducted a phase I study to determine the recommended dose of thalidomide combined with melphalan plus prednisolone (MPT) and a phase II study evaluating the efficacy and safety of this MPT regimen in transplant-ineligible Japanese patients with untreated multiple myeloma. The recommended dose was determined to be 100 mg/day in the phase I study. In the phase II, randomized, double-blind, parallel-group study, patients were allocated to either MPT (n = 52) or MP (n = 51), with 21 and 29 patients completing the study, respectively. Overall response rate, the primary endpoint, was significantly higher in the MPT [40.4% (21/52 patients), 95% confidence interval (CI) 27.0-54.9%] than in the MP [19.6% (10/51 patients), 95% CI 9.8-33.1%] group (P = 0.022). Time to response was also significantly shorter in the MPT group. Incidences of hematological toxicities were similar in the two groups, suggesting that addition of thalidomide did not increase hematological toxicity. Although incidences of some non-hematological toxicities tended to be higher in the MPT group, the low incidence of ≥ Grade 3 toxicities suggests that MPT therapy was well tolerated. These results support the safety and efficacy of MPT therapy in untreated Japanese multiple myeloma patients.