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CFU—GM are not increased in peripheral blood of patients with chronic lymphocytic leukaemia

To the Editor: In a recent issue of the European Journal of Haematology, Tsatalas and co-workers reported that, in their experience, peripheral blood CFUGM were markedly increased in patients with Bcell chronic lymphocytic leukemia (CLL) (1). This finding was irrespective of time of evaluation, treatment, clinical stage and pattern of neoplastic bone marrow infiltration, with the sole possible exception of cases with high (>60x109/1) peripheral blood lymphocytosis (PBL). The authors concluded that such an observation could stimulate the use of autologous peripheral blood stem cell (PBSC) transplants in patients with CLL. We evaluated the presence of circulating CFUGM in a representative group of 15 CD5+/CD23+ B-CLL (11 males and 4 females; mean age 63.7 yr, range 50-87) in various phases of disease (diagnosis, progression or remission after treatment, stable disease without therapy). In the clonogenic assay employed we used IMDM-methylcellulose cultures containing 30% fetal calf serum, 10% bovine serum albumin, 50 ng/ ml GM-CSF, 50 ng/ml G-CSF and lo4 pl/ml betamercapto-ethanol. A total of 5x105 cells were plated in 35-mm Petri dishes and incubated at 37°C in a humidified atmosphere of 5% CO, in air. CFU-GM were counted in duplicate after 14 d, with an inverted microscope. In our series, no patient showed more than 12 CFU-GM (expressed as mean of 2 dishes) in peripheral blood, while in 8 cases no CFU-GM could be observed (mean 2.4). Such results were not affected by clinical phase, stage, treatment (chlorambucil or fludarabine), marrow histology or PBL (Table 1). In a control group of 25 healthy donors, the CFU-GM count was in the range of 515 (mean 8.3).Thus, we found that CLL patients display a number of circulating CFU-GM lower than normal subjects. Some differences, such as the clonogenic tests employed (in particular the use of recombinant growth factors instead of lymphocyte chronic lymphocytic