Autologous peripheral blood stem cell transplantation in acute myeloblastic leukaemia and myelodysplastic syndrome patients: evaluation of tumour cell contamination of leukaphereses by cytogenetic and molecular methods.

We evaluated 18 acute myeloblastic leukaemia (AML) and myelodysplastic syndrome (MDS) patients with abnormal karyotype at diagnosis who underwent peripheral blood stem cell (PBSC) transplantation. To evaluate the presence of residual tumour cells, bone marrow (BM) samples and PBSC collections were analysed by cytogenetics and in selected cases also by fluorescence in situ hybridisation (FISH) and molecular studies. All patients were considered to be in morphologic and cytogenetic complete remission (CR) at the time of mobilisation. Seven patients showed neoplastic cells in PBSC harvest and/or BM specimen before reinfusion. Cytogenetic studies revealed contamination in apheretic collections in one patient only, while three patients had BM but not PBSC contamination. Three more patients had leukaemic cells both in the BM and PBSC. All but one (with only BM contamination) of these patients relapsed within 9 months. However, five more patients relapsed after transplantation: in four cases there was no cytogenetic sign of contamination either in PBSC or BM cells and in one case no molecular evidence was revealed either. This study suggests that, whereas the presence of leukaemic cells in autologous grafts correlates with a poor prognosis, the lack of detection of tumour cells is not always predictive of long-term disease-free survival. More importantly, PBSC collections from AML patients are not contaminated by leukaemic cells if the BM is disease-free.