MOLECULAR-DETECTION OF TUMOR CONTAMINATION IN PERIPHERAL-BLOOD STEM-CELL HARVESTS

A total of 96 peripheral blood stem cell harvests (PBSCH) were collect ed following standard chemotherapy from 27 patients with leukemia, lym phoma, and myeloma. Tumor molecular markers were analyzed in diagnosti c samples by Southern blot [immunoglobulin heavy chain (IgHJ), T cell receptor (TcR) delta chain, TcR beta chain] and polymerase chain react ion (PCR) amplification [IgH, TcR delta, t(14;18) translocation] and f ound in 11 of 22 and 13 of 27 patients, respectively. At a sensitivity of 2 to 5%, Southern blot analysis failed to detect tumor in PBSCH. U sing PCR with sensitivities of 10(-4) (IgH, TcR delta) to 10(-6) [t(14 ;18)] tumor was present in 34 PBSCH collected from five patients with acute lymphoblastic leukemia and two with lymphoma. In these patients, PBSCH collected after successive courses of chemotherapy remained con sistently positive. However, no tumor was detected in 28 PBSCH from fi ve patients with lymphoma and one with myeloma. Of eight patients who had bone marrow examined (six concurrently) within 3 weeks of PBSCH, o ne had tumor in the PBSCH but not in the bone marrow, and three had tu mor in the bone marrow but not in the PBSCH, indicating a possible adv antage in using PBSC for autologous transplantation in these patients. Although PBSC are an alternative source of stem cells to bone marrow and are considered to have a lower incidence of tumor contamination, t he majority of PBSC in this study were positive by PCR analysis. PCR a nalysis was unable to determine if a positive result represents clonog enic cells capable of initiating relapse following transplant.