Apheresis Safety and Product Yield among Elderly Donors for Allogeneic Sibling Hematopoietic Cell Transplantation (HCT).
Authors: Abdalla Ghada , Guthrie Katherine A. , Sorror Mohamed L. , Linenberger Michael 
Published: October 2019

Abstract
With the advent of reduced-intensity conditioning regimens and the improved supportive care after high-intensity conditioning, elderly patients are increasingly offered allogeneic HCT using peripheral blood stem cells (PBSC) from older siblings. Little is known, however, about the potential impact of pre-collection medical fitness on the safety of the apheresis procedure and product yield with elderly donors. To address these issues, we reviewed the experiences of 140 sibling PBSC donors with a median age of 64 (range 60–83) who underwent collection between 1993 and 2006. About half of the donors were male. All donors were mobilized using granulocyte colony-stimulating factor, at 16 mg/kg/day, and underwent 12-liter apheresis procedures. Pre-apheresis medical comorbidities were scored by the HCT-specific comorbidity index (HCT-CI, Sorror et al. Blood.2005; 106, 2912–2919) and post-apheresis toxicities were graded per the Common Toxicity Criteria of National Cancer Institute. Donors acquired HCT-CI scores of 0 (62%), 1 (20%), 2 (8%), 3 (9%), and ≥4 (1%). Eighty-four percent of donors underwent 2 PBSC collections (roughly half were mandatory) and 18% required 3 collections. A central venous catheter (CVC) was placed in 27 elderly donors (19%), and 28% of those requiring 3 collections had a CVC. There was no difference in the median age of donors requiring a CVC compared to those who did not. Longer apheresis procedure times were required during the 3rd collection (median of 149 minutes) compared to the 1st (136 minutes) and 2nd collections (131 minutes). Among the 15 donors with three procedures, significantly fewer CD3+ cells were collected across time (median of 1.7, 1.2, and 0.7 × 108 cells/kg recipient weight after the 1st, 2nd, and 3rd collections, respectively, p<0.001). There was a decreasing trend in both CD3+ and CD34+ cell yields across groups of donors with increasing numbers of collections (p<0.001 for both). Donors with HCT-CI scores of ≥3 had higher, but non-significant, median age (67 years) compared to those with scores of 0, 1, and 2 (64, 62, and 63, respectively). There were no correlations between increasing donor age above 60 years and procedure-related toxicities of grades ≥I (p=0.62) or ≥II (p=0.62). Donors with comorbidity scores of 2 or ≥3 had slightly higher incidence rates of grades ≥I toxicities (55% and 57%) compared to donors with scores of 0 and 1 (40% and 48%; p=0.16). There were no correlations between increasing donor age above 60 years and pre-collection white blood cell counts (p=0.31), apheresis procedure times (p=0.41), CD34+ cell yields (p=0.24), and CD3+ cell yields (p=0.26). We conclude that: 1) apheresis collection of PBSC is a safe procedure for donors with an age of ≥60 years, including those with medical comorbidities; 2) among elderly donors, increasing age did not significantly affect the need for CVC, risk of procedure-related toxicity or product yields; 3) sequential collections yield fewer CD3+ cells among donors of this age category. These latter findings need to be compared to those from multiple collections among donors with younger age. In addition, it will be important to compare the engraftment capacity of the PBSC products from elderly versus younger donors.