Peripheral blood stem cell transplants for multiple myeloma: identification of favorable variables for rapid engraftment in 225 patients

Transfusion of autologous peripheral blood stem cells (PBSCs) of good quality ensures fast hematopoietic engraftment after myeloablative therapy with a decrease in procedure-related morbidity and mortality. We have analyzed variables influencing the kinetics of engraftment, and therefore reflecting the quality of PBSC collections, in 225 patients with newly diagnosed or refractory multiple myeloma (MM) who received an autotransplant in support of high dose melphalan (200 mg/m2); 132 of these patients also completed a second transplant. All PBSCs were collected before the first transplant after high-dose cyclophosphamide (6 g/m2) and hematopoietic growth factors, mainly granulocyte-macrophage colony-stimulating factor. PBSCs were administered either alone (91 patients) or with bone marrow (134 patients). A highly significant correlation was observed between the number of CD34+ cells per kilogram infused and prompt recovery of both granulocytes (P = .0001) and platelets (P = .0001). After correction for the proportion of patients with > or = 2 x 10(6)/kg CD34 PBSCs infused and with < or = 12 months of prior therapy, no difference in engraftment kinetics was seen between patients receiving PBSCs only and those also receiving bone marrow. Exposure to chemotherapy, even to < or = 6 months of alkylating agents, significantly delayed hematopoietic recovery posttransplantation. The threshold dose of CD34 cells necessary for prompt engraftment was > or = 2.0 x 10(6)/kg for patients with < or = 24 months of chemotherapy before the first transplant, whereas greater than 5 x 10(6)/kg CD34 cells were required to assure rapid recovery also in those with longer exposure. Such quantities, easily collected in the large majority of patients with shorter exposure (91%), were obtained in only 28% of patients with more than 24 months of prior chemotherapy. Rapid platelet recovery within a narrow range of time (before day 14) was almost invariably seen (94%) when greater than 5 x 10(6)/kg CD34 cells were infused, irrespective of the duration of prior therapy, whereas the range widened progressively when less CD34 cells were infused. In the absence of CD34 measurements, fast recovery of platelets to greater than 50 x 10(9)/L within 14 days after high-dose cyclophosphamide and < or = 12 months of prior chemotherapy were the best predictors of early engraftment. Prudent use of stem cell-damaging agents, such as melphalan and nitrosoureas, is recommended in MM patients who might be candidates for autotransplantation. Alternatively, PBSCs should be collected early after diagnosis.