Marrow transplantation for malignant plasma cell disorders: summary of the Seattle experience

28 patients with plasma cell malignancies received marrow transplants from identical twins (N = 8), HLA-identical family members (N = 15), HLA partially-matched relatives (N = 3) or cryopreserved autologous marrow (N = 2). Treatment regimens included cyclophosphamide (CY) and total body irradiation (TBI) for 15 patients and busulphan (BU) and CY for 13 patients. 3 of 8 twins are alive, 2 without disease at 24 and 34 months, and 1 is alive and well at 116 months without evidence of disease except for at small residual monoclonal protein spike. 12 of the 18 allografted patients died of transplant-related causes and 2 died of progressive disease. 4 of 18 allograft recipients are alive; 2 are free of disease at 16 and 15 months, 1 is alive at 6 months without disease except for persistent monoclonal Kappa protein. 1 patient is alive with residual marrow involvement and a persistent IGA lambda monoclonal protein at 7 months. 1 of the 2 autograft recipients is alive 2 months after transplant and is not yet evaluable for tumor response and the other patient died early of transplant-related complications. Both CY + TBI and BU + CY resulted in remissions in patients with advanced plasma cell malignancies. However, the optimal treatment regimen and timing of transplantation remain to be determined.