Spleen enlargement following recombinant human granulocyte colony-stimulating factor administration for peripheral blood stem cell mobilization

Background and Objectives. Recombinant human granulocyte colony-stimulating factor (rhG-CSF) is widely to mobilize peripheral blood stem cells (PSBC) for autologous or allogenic transplants. Such treatment may cause spleen enlargement; exceptionally, spontaneous spleen rupture has been reported. We investigated changes in spleen size during stem cell mobilization. Design and Methods. We evaluated spleen size, comparing palpation with ultrasound (US)-evaluated longitudinal diameter and volume, in 13 healthy donors and 22 patients with a hematological malignancy who were undergoing PBSC mobilization with rhG-CSF-including regimens. Results. Intraobserver and interobserver variability of US-calculated spleen volume was very low; the correlation between the volume calculated by US and that measured by 3-dimensional computed by US and that measured by 3-dimensional computed tomography was excellent. During mobilization, spleen enlargement was detected by palpation in 17% of subjects, by US-measured longitudinal diameter in 60%, and by US-calculated volume in 91%. The median increase in spleen volume was 300 nL (range, 54-820; p<0.001) in healthy donors and 135 mL (range, 0-413; p=0.004) in the group of patients; the enlargement correlated with white blood cell count elevation (p=0.016) but not with circulating CD34(+) cells. One month after the last administration of rhG-CSF, the median decrease was 160 mL (range, 35-800) in healthy donors and 58 mL (range, 0-310) in patients. Interpretation and Conclusions. When evaluated by sensitive methods, rhG-CSF caused spleen enlargement in almost all individuals treated. US-calculated volume proved to be an excellent method, much better than longitudinal diameter, for detecting non-palpable splenomegaly induced by rhG-CSF.