A comparison of toxicity following two different doses of cyclophosphamide for mobilization of peripheral blood progenitor cells in 116 multiple myeloma patients.

High-dose cyclophosphamide (HDC) has been shown to be an effective regimen for collecting PBPC in multiple myeloma (MM) patients, but the optimal dose to be used remains controversial. Two historical cohorts of MM patients who received G- or GM-CSF and HDC at the dose of either 7 g/m(2) (HDC7, n = 74) or 4 g/m (HDC4, n = 42) were compared. As patients in the HDC4 group were more likely to have received G-CSF than GM-CSF (P < 10(-3)) and fewer previous alkylating agents (P = 0.004), multivariate logistic regression analysis was performed. In the HDC4 group, patients had a shorter median duration of neutropenia (P < 10(-4)), fewer RBC (P < 10(-3)) and platelet transfusions (P < 10(-3)) with fewer patients with platelets <20 x 10(9)/l (P = 0.004). Moreover, fewer febrile episodes (P < 10(-3)) and less need of intravenous antibiotics (P < 10(-3)) were found in the HDC4 group. No statistical difference was observed with regard to CD34(+) cell collection efficiency. Thus, the use of HDC at the dose of 4 g/m(2) for the collection of PBPC in MM patients decreases hematological and extrahematological toxicity with an equivalent CD34(+) cell collection efficiency.