Autotransplants in multiple myeloma: what have we learned?

Of 496 consecutive patients with multiple myeloma (MM) enrolled in clinical trials of tandem transplants with peripheral blood stem cells support, 470 (95%) completed the first autotransplant with melphalan 200 mg/m2 (MEL 200) and 363 (73%) completed the second transplant with either MEL 200 (40%), MEL 140 mg/m2 (MEL 140) with total-body irradiation (17%), or a combination of alkylating agents (16%), depending on the response status prior to the second transplant; 31 patients up to age 60 years received an allograft as the second transplant. The median interval from first to second transplant was 5 months. Treatment-related mortality during the first year after transplantation was 7%, and complete remission (CR) was obtained in 36%; the median durations of event-free survival (EFS) and overall survival (OS) after transplant were 26 and 41 months, respectively. Low beta 2-microglobulin ([B2M] < or = 2.5 mg/L) and C-reactive protein ([CRP] < or = 0.4 mg/dL) were the most significant standard parameters associated with both prolonged EFS and OS. Median OS exceeded 5.5 years in the one third of patients with both low B2M and CRP. When cytogenetics were included in the analysis, the presence of 11q abnormalities and/or complete or partial deletion of chromosome 13 ("unfavorable karyotype") became a dominant negative feature for both EFS and OS. In addition to these pretransplant parameters, attainment of CR and application of two transplants within 6 months both significantly extended EFS and OS. The group of patients (7%) with high B2M and CRP with either IgA isotype or unfavorable karyotype had the worst prognosis (EFS, < or = 10 months; median OS, < or = 12 months) and will require novel therapy. We conclude that tandem transplants are feasible in the majority of patients up to age 70 years, effecting CR in one third of all patients. Median OS was greater than 5.5 years, regardless of pretransplant features, if the first transplant was applied within 12 months of initial treatment and the second transplant no more than 6 months later.