PB2329 THE IMPACT OF VITAMIN D LEVELS ON PERIPHERAL STEM CELL MOBILIZATION IN ALLOGENEIC HEMATOPOIETIC STEM CELL DONORS

Background: Vitamin D is a steroid hormone which has an essential role in many physiological conditions including bone metabolism, immune regulation and hematopoiesis. Vitamin D was indicated to have a favourable impact on hematopoietic stem cell (HSC) production in in‐vitro studies. Additionally, animal experiments designated a potential for vitamin D receptor in HSC mobilization. Despite these advances, the possible role of vitamin D in peripheral HSC mobilization remains to be defined. Aims: The aim of this study was to evaluate the impact of pre‐mobilization serum vitamin D levels on peripheral HSC mobilization in allogeneic donors. Methods: We investigated the impact of pre‐mobilization serum vitamin D levels of 112 allogeneic donors [median age: 39(18‐69) years; male/female: 62/50] on peripheral HSC mobilization. All donors had received granulocyte colony stimulating factor (G‐CSF) at a dose of 10 mcg/kg/day for 4 days. First HSC apheresis was performed on the fourth day of G‐CSF. Serum 25‐hydroxy vitamin D levels were measured with immunoassay method before G‐CSF administration. Results: M edian vitamin D level was found to be 15.8(3‐63.2) μg/L in the study population. On the first apheresis day, median peripheral and product CD34(+) cell counts were 36.5(7‐206) × 10 6 /kg and 5.3(0.5‐22.8) × 10 6 /kg respectively. Median vitamin D levels were significantly lower in donors with low peripheral CD34(+) cell count which was defined as <20 × 10 6 /kg, compared to donors with CD34 level≥20 × 10 6 /kg [13.5(7‐27.4) μg/L vs 17(3‐63.2) μg/L; p = 0.035] (Figure 1). When we divide the study group into two subgroups based on median vitamin D levels, peripheral CD34(+) cell counts were found to be significantly lower in low‐vitamin D group compared to high‐vitamin D group [35(7‐135) × 10 6 vs 41.4(10‐206) × 10 6 ; p = 0.038]. Any significant association was not observed between vitamin D levels and product CD34(+) cell counts. In logistic regression analysis, serum vitamin D level was considered to be correlated with peripheral CD34(+) cell count [p = 0.042; SE: 0.034; 95% Cl Exp(B): 1.003‐1.145]. Summary/Conclusion: Mobilization failure still remains to be a critical issue for HSC transplantation. In this study, the significant association between vitamin D levels and peripheral CD34(+) cell counts, lacking a similar correlation with product CD34(+) cell counts, requires further evaluation with larger study populations and more standardized procedures including product processing and collection. In these circumstances, the possible role of vitamin D in HSC mobilization deserves further consideration as vitamin D replacement before mobilization would be an easy, safe and cost‐effective approach to improve mobilization success.