MYELOMA CELL CONTAMINATION OF PERIPHERAL-BLOOD STEM-CELL GRAFTS IN PATIENTS WITH MULTIPLE-MYELOMA TREATED BY HIGH-DOSE THERAPY

In order to assess the contamination with malignant cells of periphera l blood stem cell (PBSC) transplants used to support high-dose therapy in multiple myeloma (MM), we used the immunoglobulin heavy chain gene radioactive fingerprinting polymerase chain reaction (PCR) method to detect clonal cells in PBSC from 10 patients. The sensitivity of the t echnique allowed the detection of one clonal cell among 10(4) normal b lood mononuclear cells. A clonal band was detected in 4 of 11 leukaphe reses samples. The level of contamination was low because a clonal ban d could never be identified on ethidium bromide-stained agarose gels w hose sensitivity is between 1 and 5%. The use of granulocyte-colony st imulatory factor (G-CSF) in combination with chemotherapy in three cas es did not seem to increase the contamination of PBSC grafts; in one p atient, G-CSF was used during a second course of leukapheresis which w as free of detectable clonal cells whereas the first one performed aft er chemotherapy alone contained clonal cells. Thus, PBSC grafts may ra rely be completely devoid of clonal potentially malignant cells but th e level of contamination is much lower than in BM grafts. Whether graf t contamination is an important adverse prognostic factor for patients with MM undergoing intensive treatment and autografting is still unse ttled.