COMPARISON OF MYELOMA CELL CONTAMINATION OF BONE-MARROW AND PERIPHERAL-BLOOD STEM-CELL HARVESTS

It could be speculated for patients with myeloma and other lymphoproli ferative disorders that peripheral blood stem cells may be preferable to bone marrow for autologous transplantation because they may be less contaminated by neoplastic cells. To test this possibility, the immun oglobulin heavy chain gene rearrangement and limiting dilution polymer ase chain reaction were used to sensitively quantify myeloma cells in bone marrow and peripheral blood stem cell collections, taken at a sim ilar time, from eight patients with multiple myeloma. Levels of residu al disease in the peripheral blood stem cell harvests were variable an d did not reflect the tumour burden in the marrow. Peripheral blood st em cells contained 1.7 to 23 700-fold fewer myeloma cells compared wit h the bone marrow and would have resulted in reinfusion of 0.08 to 59 480-fold fewer myeloma cells based on total reinfused CFU-GM and 0.24 to 24 700-fold fewer myeloma cells based on total reinfused nucleated cells, Assuming that the proportion of clonogenic myeloma cells is equ ivalent, peripheral blood stem cells may be better than bone marrow as a source of haemopoietic stem cells for transplantation in multiple m yeloma. The clinical followup suggested that patients transplanted wit h peripheral blood stem cells containing a low number of myeloma cells had better disease control than those transplanted with peripheral bl ood stem cells containing a high number.