High-risk multiple myeloma treated with high-dose melphalan.

PURPOSE: This study was undertaken to evaluate the efficacy and toxicity of high-dose melphalan (HDM) 140 mg/m2 in poor-risk multiple myeloma (MM). PATIENTS AND METHODS: Thirteen patients were previously untreated, and 13 had been pretreated with vincristine, Adriamycin (doxorubicin; Adria Laboratories, Columbus, OH), and dexamethasone (VAD) for refractory or relapsed MM. RESULTS: All 11 fully assessed, untreated patients responded, and six achieved a complete response. Remissions were of excellent quality, but response duration--a median of 16 months--was short. This was probably due to the high incidence of unfavorable prognostic signs, like a high beta 2-microglobulin (B2M) and/or a high plasma cell labeling index (LI). None of the nine pretreated patients with a measurable M component had more than 50% reduction of M component after HDM, indicating that intensive treatment has no effect on a residual tumor population. The relapse-free period after HDM in this group of patients (median, 9 months) was not better than in a historical control group of patients treated with VAD alone. The major complications due to the prolonged myelosuppression were severe infections. After primary HDM, median time to recovery to greater than 0.5 x 16(9) granulocytes was 30 days; in previously treated patients, the recovery period was even longer. There were three toxic deaths. Fulminant relapses with features of J-chain disease were frequently observed, indicating a dedifferentiated tumor, probably induced or selected by the HDM. CONCLUSIONS: HDM is an effective treatment resulting in good remissions for untreated MM. However, other therapy strategies should be explored first, focusing on the reduction of toxicity and prolongation of the relapse-free period, before HDM can be recommended as first-line treatment for the younger MM patient.