QUANTITATIVE COMPARISON OF MULTIPLE-MYELOMA TUMOR CONTAMINATION IN BONE-MARROW HARVEST AND LEUKAPHERESIS AUTOGRAFTS

Autologous transplantation is increasingly being used to treat patient s with multiple myeloma (MM). Recently, peripheral blood progenitor ce ll (PBPC) harvests have been preferred over autologous bone marrow (BM ) harvests due to reduced engraftment time, ease of attainment, and pr esumptive reduction of occult tumor involvement, To resolve this latte r assumption quantitatively, we have used the unique immunoglobulin (I g) heavy chain variable region sequence of the patient's myeloma cell as a marker of clonality, Samples from PBPC collections and 'back-up' BM harvests were obtained from 13 patients with MM and analyzed for tu mor contamination using patient-specific oligonucleotide primers and t he polymerase chain reaction, As expected, the percentage of tumor cel ls contaminating the BM harvest (median, 0.74%) was higher than in the PBPC specimens (median, 0.0024%), Because of the increased total numb er of cells required for PBPC transplantation, the increase in total n umber of contaminating cells in the BM vs PBPC autografts was less pro nounced, (BM:PBPC tumor contamination ratios ranging from 0.9 to >4500 ; median, 14), This confirms that in most but not all cases unmanipula ted PBPC products are preferable over BM harvests as a method of reduc ing myeloma autograft tumor contamination.