Autologous Bone Marrow Transplantation - Blog Science Connections

16 Purged ABMT in CR of Acute Leukemia
consolidation therapy for adults with acute leukemia in remission. We had two
goals: 1) to treat each patient's marrow with the highest possible dose of
mafosfamide to achieve maximum antileukemic activity, but also to spare
enough normal stem cells for successful engraftment; and 2) to assess the
potential benefit of high-dose consolidation treatment followed by ABMT with
cleansed marrow, in terms of duration of remission and disease-free survival.
We report here the current status of our clinical trial with 57 patients treated
while they were in CR with CY and total body irradiation (TBI), followed by the
reinfusion of autologous bone marrow treated with mafosfamide at a dosage
predetermined to spare 5% colony-forming units granulocyte-macrophage
(CFCJ-GM LD 95
).
MATERIALS AND METHODS
Details on in vitro studies, determination of the dose of mafosfamide for
each patient (by preincubation test [ PIT]), marrow incubation, marrow freezing,
pretransplant regimen, and ABMT procedure have been described previously
along with the preliminary clinical results in a first series of 24 patients (7). In
short, for each patient's PIT a 10-ml marrow aspirate was taken 15 days before
bone marrow collection. The sensitivity of remission CFCJ-GM to increasing
doses of mafosfamide was studied and a dose-response curve established. The
optimal dose for later incubation of the marrow was defined as the dose sparing
5% CFU-GM as measured by the PIT. This dose was selected from previous
continuous liquid culture studies as the highest possible dose that would spare
enough normal stem cells to ensure consistent engraftment; the residual
amount of 5% CFCI-GM was considered a safe margin beyond which further
cytotoxicity would not be measurable, at least by conventional laboratory
means.
Marrow collection took place in patients in CR after one to three
consolidation courses. A total volume of 600-1,300 ml of bone marrow was
collected from the posterior iliac crests under general anesthesia. A volume
corresponding to 0.5 x 10 8
nucleated cells/kg was saved and directly
cryopreserved to serve as a back-up marrow. The remaining volume was further
processed with mafosfamide for incubation. The buffy coat was collected on a
Haemonetics H-30 cell separator (Haemonetics, Plaisir, France) and adjusted
withTC 199 medium to a final cell concentration of 2 x 10 7
cells/ml with a final
hematocrit of 5%. The suspension was finally incubated with mafosfamide, at
the concentration previously established from the PIT, for 30 minutes in a water
bath at 37°C and with gentle shaking. In the freezing procedure, dimethyl
sulfoxide was used at a final concentration of 10% in TC 199 medium, Tefloncapton
DF 1000 Gambro bags (Gambro, Paris, France), and a Nicool 316
programmed biological freezer (CFPO, Sanssenage, France). The cooling
program followed modern principles of stem-cell cryopreservation, as described
by us and others (8).