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Pretreatment With Alkylating Agents<br />

Predicts for Tumor Cell Content <strong>and</strong><br />

CD34+ Stem Cell Yield in Leukapheresis<br />

Products of Patients With Multiple Myeloma<br />

K. Kiel, M. Moos, F.W. Cremer, E. Ehrbrecht, A. Benner<br />

U. Hegenbart, R. Haas, Y. Ko, A.D. Ho, H. Goldschmidt<br />

Department of Internal Medicine V (K.K., F.C., EE., U.H., R.H., M.M., H.G.),<br />

University of Heidelberg; Department of Internal Medicine (Y.K.), University<br />

of Bonn; German Cancer Research Center (A.B.), Heidelberg, Germany<br />

ABSTRACT<br />

The aim of our study was to examine whether pretreatment regimens affect the<br />

tumor load <strong>and</strong> the stem cell yield in leukapheresis products (LP) of patients with<br />

multiple myeloma (MM) harvested after high-dose cyclophosphamide <strong>and</strong><br />

granulocyte colony-stimulating factor (G-CSF). We assessed the percentages of<br />

tumor cells <strong>and</strong> CD34 +<br />

cells in LP collected on day 1 (LP 1) from 30 patients with<br />

MM. The proportion of clonotypic cells was quantitated by an allele-specific<br />

oligonucleotide (ASO) polymerase chain reaction (PCR) assay based on limiting<br />

dilutions. CD34 +<br />

cells were determined by flow cytometry. The percentages of<br />

malignant cells in the LP were in the range of 0.0 to 0.71% (mean 0.04%). CD34 +<br />

cells ranged between 0.1 <strong>and</strong> 9.72% (mean 2.05%). We could demonstrate for the<br />

first time that conventional therapy with alkylating agents was able to significantly<br />

lower the tumor numbers of the first leukapheresis collected (Spearman test: total<br />

number of cycles with alkylating agents, />=0.035; pretreatment with alkylating<br />

agents in the last three cycles before mobilization, P=0.016). Pretreatment with<br />

alkylating agents (kind <strong>and</strong> number of pretreatment cycles) also significantly reduced<br />

the stem cell yield (/^O.OOCKM, P=0.0004, respectively). Thus, the positive impact of<br />

pretreatment with alkylating agents in lowering the tumor load in apheresis products<br />

must be balanced against the adverse effect on the stem cell yield.<br />

INTRODUCTION<br />

MM is a B cell malignancy characterized by the accumulation of clonal plasma<br />

cells in the bone <strong>marrow</strong> (BM) secreting a monoclonal immunoglobulin.<br />

235

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