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 a case-matched study, response rate and event-free survival of MEL200 were superior to MEL100, but overall survival (OS) was similar. In this prospective, randomized, phase III trial, we compared the efficacy and toxicity of MEL200 and MEL100. Between January 2002 and July 2006, 299 patients were enrolled. Inclusion criteria were previously untreated myeloma, aged < 65 and Durie and Salmon stage II or III. Exclusion criteria were abnormal cardiac function, respiratory disease, abnormal liver function, abnormal 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 dexamethasone-doxorubicin-vincristine debulking courses (doxorubicin 50 mg/m² day 1, vincristine 1 mg day 1, dexamethasone 40 mg days 1, 2, 3, 4, each course repeated every 28 days), 2 cycles of cyclophosphamide (4 g/m², day 1) plus G-CSF followed by stem cell harvest. The MEL200 group was conditioned with 2 cycles of melphalan 200 mg/m² followed by stem cell reinfusion; the MEL100 group was conditioned with 2 courses of melphalan 100 mg/m² followed by stem cell reinfusion. At the present, 246 patients, median age 57 (range 32–65), completed the assigned therapy and were evaluated for response, progression-free survival (PFS) and OS. One-hundred and twenty-four patients were randomized to MEL200 and 122 to MEL100. Patient characteristics were similar in both groups. Abnormal cytogenetics (13q deletion, t(4;14), t(11;14), p53) were 75% in MEL200 patients and 56% in MEL100 patients (p=0.05). Forty-six patients did not complete tandem MEL200; 36 patients did not complete tandem MEL100. The near complete response rate of MEL200 was superior to MEL100 (32% versus 18%, p=0.011), but partial response was 80% versus 71%, respectively (p=0.079). The median follow-up for censored patients was 26.5 months. The 3 years PFS was 51% in the MEL200 arm and 33% in the MEL100 arm (HR=0.81, 95% CI 0.55–1.21, p=0.31). The 3 years OS was 86% in the MEL200 group and 71% in the MEL100 group (HR=0.82, 95 CI 0.45–1.48, p=0.51). Duration of grade 4 neutropenia and thrombocytopenia was comparable in two arms, but MEL200 patients required more platelet transfusions (p=0.03). Grade 3–4 non-hematological adverse events were reported in 49% of the MEL200 patients and in 38% of the MEL100 patients (P=0.07). The most frequent grade 3–4 adverse events were infections (54% of MEL200 patients versus 45% of MEL100 patients, p=0.25), mucositis (31% of MEL200 patients versus 7% of MEL100 patients, p=0.002) and gastrointestinal toxicities (20% of MEL200 patients versus 14% of MEL100 patients, p=0.3). In conclusion, MEL200 resulted in a significantly higher near complete response rate but this did not translate in a superior PFS and OS.