A Prospective, Randomized, Phase III Study of Melphalan 200 mg/m² (Mel200) Versus Melphalan 100 mg/m² (Mel100) in Newly Diagnosed Myeloma Patients.

Several trials have shown the superior impact of high-dose melphalan (usually 200 mg/m², MEL200) versus standard therapy in myeloma patients. Intermediate-dose melphalan (100 mg/m², MEL100) was also superior to the standard dose, but MEL100 has not been clinically compared with MEL200 in a randomized study. In this prospective, randomized, phase III trial, we compared the efficacy and toxicity of MEL200 and MEL100. The primary end points were complete remission (CR) rate, event-free survival (EFS) and incidence of gastrointestinal toxicity, infections and treatment-related mortality (TRM). Inclusion criteria were previously untreated myeloma, aged ≤ 65 and Durie and Salmon stage II or III. Exclusion criteria were abnormal pulmonar, cardiac, liver and renal function, HBV, HCV, or HIV positivity, concomitant cancer or psychiatric disease. The institutional review board approved the protocol and written informed consent was obtained from all patients. All patients received 2 cycles of 28-day-dexamethasone-doxorubicin-vincristine (doxorubicin 50 mg/m² day 1, vincristine 1 mg day 1, dexamethasone 40 mg days 1–4) and 2 cycles of cyclophosphamide (4 g/m², day 1) followed by stem cell harvest. MEL200 patients was conditioned with 2 cycles of melphalan 200 mg/m² and MEL100 patients with 2 courses of melphalan 100 mg/m², both followed by stem cell reinfusion. Two-hundred and ninety-eight patients (median age 57) were randomized, 149 to MEL200 and 149 to MEL100. All patients were evaluated for response, EFS and OS. Patient characteristics were similar in both groups. Chromosomal 13 was deleted in 69% of MEL200 and 45% of MEL100 patients (p=0.015). Ninety-six patients completed tandem MEL200; 103 tandem MEL100. In intention-to-treat analysis, the very good partial response rate was higher in MEL200 group (37% versus 21%, p=0.003), but CR was 15% in the MEL200 group and 8% in the MEL100 group (p=0.07). After a median follow-up of 30.5 months, the 3-years EFS was 46% in the MEL200 and 26% in the MEL100 group (HR=0.7, 95% CI 0.51–0.97, p=0.03). The 3-years overall survival (OS) was 81% in the MEL200 and 73% in the MEL100 group (HR=0.69, 95% CI 0.42–1.13, p=0.14). Duration of grade 4 neutropenia and thrombocytopenia was comparable, but a higher proportion of MEL200 patients required platelet transfusions (p=0.002). Grade 3–4 non-hematologic adverse events were more frequent in the MEL200 patients (38% versus 19%, p<0.0001). The incidence of grade 3–4 mucositis was 16% after MEL200 and 3% after MEL100 (p<0.0001). The incidence of severe gastrointestinal toxicity was 19% after MEL200 and 2% after MEL100 (p<0.0001). The incidence of grade 3–4 infections and of TRM was similar in both groups. In conclusion, MEL200 resulted in a significantly higher very good partial response rate. This translated in a superior EFS, but not OS.