Detection of minimal residual disease in hematopoietic progenitor cell harvests: lack of predictive value of peripheral blood and bone marrow analysis in mantle cell and indolent lymphoma.

Elimination of neoplastic cells from peripheral blood progenitor cells (PBPCs) is an important issue in transplantation-based high-dose chemotherapy in non Hodgkin's lymphoma (NHL). The capacity to reliably assess the presence of residual lymphoma cells in PBPCs is mandatory in designing this type of protocols. Polymerase chain reaction (PCR) amplification of molecular rearrangements is widely used to detect minimal residual disease (MRD) in NHL patients. Although concordant data can be obtained in most of the cases from peripheral blood (PB) and bone marrow (BM) at diagnosis, the relationship between these two compartments and the role of their analysis in predicting the molecular status of PBPCs is still an open issue. Here we report data about MRD analysis in BM, PB and PBPCs in a series of mantle cell and indolent NHL patients who underwent high-dose chemotherapy: discordant results were obtained comparing PB, BM and PBPC molecular data. In addition, differences were noted among these results if molecular analysis was performed using well-known rearrangements (i.e., bcl-1/IgH and bcl-2/IgH) or patient specific oligonucleotides. We conclude that neither BM nor PB are reliable in predicting the molecular status of PBPCs and that caution must be adopted in interpreting molecular data obtained using patient specific oligonucleotides.