Comparison of four cytokine regimens for mobilization of peripheral blood stem cells: IL-3 alone and combined with GM-CSF or G-CSF

Improved methods for mobilization may reduce the number of aphereses required to collect adequate numbers of peripheral blood stem cells (PBSC) and hasten engraftment following high-dose therapy. Mobilization with cytokines alone enables engraftment after myeloablative therapy. The optimal cytokine regimen for mobilization has not been established. The study evaluated the effects of four interleukin-3-containing cytokine regimens administered during steady state hematopoiesis on PBSC mobilization in 30 patients with breast cancer or lymphoid malignancies. These regimens included IL-3 alone (Arm 1), sequential IL-3 → G-CSF (Arm 2), sequential IL-3 → GM-CSF (Arm 3) and combined IL-3 + G-CSF (Arm 4). Consecutive days of apheresis were performed until a target of 4-6 x 10⁸ mononuclear cells/kg were collected. All patients received intravenous GM-CSF after PBSC infusion. Median days to an ANC ≥ 500/μl in Arm 3 (22 days) was significantly slower than for patients in Arm 2 (13 days) but not significantly different from patients in Arm 1 or Arm 4. There was no significant difference in platelet engraftment or days of hospitalization between the study arms. Addition of GM-CSF to IL-3-containing mobilization regimens results in collection of PBSC that lead to delayed engraftment. Further development of Arms 1, 2, and 4 appear warranted.