The relationship between monoclonal myeloma precursor B cells in the peripheral blood stem cell harvests and the clinical response of multiple myeloma patients

Abstract

The aim of this study was to determine the presence of monoclonal myeloma precursor B cells in peripheral blood stem cell harvests and to investigate their role in the clinical outcome of multiple myeloma patients. A total of 39 multiple myeloma patients were treated with a sequential therapy including double high‐dose melphalan therapy followed by a double transplant procedure. The apheresis products for the second transplant were purged using a panel of four or five different mouse monoclonal antibodies against B‐cell antigens (CD10, CD19, CD20, CD22 and CD37). In 19/39 patients a tumour‐specific CDR III signal was identified in the diagnostic bone marrow. Gene scan analysis after CDR III PCR of the magnetic bead isolated B‐cell fraction from the apheresis products in these 19 patients revealed three different patterns: 32% of patients had a predominantly monoclonal B‐cell population; 63% of patients had an identifiable monoclonal signal within an oligoclonal B‐cell population. In only 1/19 patients were no monoclonal B cells identified in the B‐cell population of the apheresis product. A correlation between the clonal pattern and the clinical response after sequential chemotherapy was found. Patients with a predominance of monoclonal myeloma or myeloma precursor B cells had an early relapse or achieved a minimal response or a partial remission. Patients with an oligo‐ and/or polyclonal pattern achieved a high percentage of partial as well as complete remissions.