Stem cell factor leads to reduced blood processing during apheresis or the use of whole blood aliquots to support dose-intensive chemotherapy.

Abstract

The addition of stem cell factor (SCF) to G-CSF and chemotherapy results in a dose-dependent, significantly increased mobilisation of peripheral blood progenitor cells compared with the use of chemotherapy and G-CSF alone. The enhanced mobilisation may benefit patients in several ways. Firstly, in clinical settings where currently multiple aphereses are having to be performed to obtain a specified target number of cells, the addition of SCF may lead to a reduction in this number. Alternatively, when only a single apheresis is currently being performed to obtain sufficient cells then the addition of SCF to the mobilisation regimen would allow between 5- and 8-fold reduction in the volume of blood required to be processed during the apheresis procedure to obtain a specified target of GM-CFC, CD34+ cells and LTC-IC for those receiving the highest dose of SCF (20 microg/kg) plus G-CSF following chemotherapy compared with those patients receiving G-CSF alone following chemotherapy. The increased mobilisation resulting from the addition of SCF to the regimen makes feasible the use of whole blood aliquots to support dose-intensive therapy. We have calculated that in patients mobilised using cyclophosphamide 3 g/m2, SCF 20 microg/kg and G-CSF 5 microg/kg a median 512 ml aliquot of whole blood would contain 2 x 10(6)/kg CD34+ cells and over 3.7 x 10(5)/kg GM-CFC. This aliquot would be sufficient to rescue the patient following a myeloablative therapy. Significantly, because less individual variation was seen after the administration of SCF the patient who showed the worst mobilisation in that group would have the usually required content of 2 x 10(6) CD34+ cells/kg and 1 x 10(5) GM-CFC/kg in only 731 ml of blood.