Time Dependent Decrease in Efficacy of Second G-CSF Mobilization in Healthy Unrelated Donors

Abstract

Introduction: Graft failure or a second allogeneic hematopoietic stem cell transplantation or HLA haplotypes leading to donor requests for two patients are reasons for a second collection of peripheral stem cells of the same donor. Few reports about second stimulation showed conflicting results. Higher G-CSF doses or the addition of plerixafor has been described either in autologous or allogenic settings. In order to get more information about second stimulation with G-CSF, we pooled the data from three collection centers in Germany.

Donors and Methods: The collection centers of Dresden, Hameln and Cologne performed between December 1991 and May 2015 18,124 collections of peripheral stem cells. We identified 351 of donors who donated twice. All collections were performed after G-CSF stimulation (Lenograstim) of 7.5 to 10 µg / kg body weight. The same apheresis machine was used in 80 % of donors. Besides Spectra and Optia from Terumo ComTec machines from Fresenius were used. We compared leukocytes, platelets, hemoglobin and CD 34 positive cells in the blood before apheresis, yield of stem cells, and blood volume processed as endpoint of interest. There are differences in the number of donor results since the reported data in the first years were incomplete. We created 4 groups of donors depending on the interval between the two donations (Group A: interval <= 90 days, group B 91 to 180 days, group C 181 to 360 days, group D > 360 days). The minimum difference between two apheresis was 20 days, the maximum 4,436 days. The data of the donors were analyzed using NCSS as statistical program. To determine significance in the data paired t tests were performed.

Results: Platelet counts, hemoglobin and erythrocyte counts at the time of apheresis was similar at first and second time point of collection. CD34-positive cells in the blood on the 1^st day of apheresis were significantly higher with 77.9/µl at 1^st apheresis compared to 67.9/µl at 2^nd apheresis. Leukocyte counts were also higher at first donation date (42,954/µl compared to 40,330/µl). Considering the product, total collected CD34 pos. cells were lower at 2^nd apheresis (617 * 10⁶ compared to 566 * 10⁶) but there was no significant difference in the CD34 pos. cells per kg BW of the patient which might be due to the observation that the body weight of the patients were lower at 2^nd transplantation. We were interested in the time-dependence of the second mobilization capacity. The details are shown in the table. Leukocyte counts in the blood remained lower after 2^nd G-CSF stimulation even after more than one year. In contrast, CD34 stimulation returned to values measured at the first stem cell collection. To achieve the requested amount of CD 34 pos. cells a higher blood volume had to be processed if the two collections are less than 6 months apart.

Discussion: Our data are in accordance with earlier observations showing that at a second stimulation with G-CSF is less affective. The data of 351 donors indicate that this difference lasts for up to 1 year for stimulation of CD34 pos. cells. Only for leukocytes, there is still a significant difference also if restimulated after more than 1 year . In contrast, this decreased restimulation of stem cells has no important clinical effect on the possibility to get suffient numbers of stem cells for a transplantation. A second treatment of a donor at least with 7.5 to 10 µg G-CSF/kg body weight does not harm the donor since baseline hematologic parameters were the same at time of medical assessment.