Predictors of Successful Allogeneic Stem Cell Donor Collection

Introduction: Transplant physicians request specific CD34 yield from donors based on the indication for alloSCT, planned conditioning regimen and use of fresh or cryopreserved stem cells. Donor Centre Try To Comply With The Transplant Centre requests, but there is increasing trend from Transplant Centres to request higher CD34 yields (>5x10⁶/kg) and currently there is insufficient information about success of mobilization with GCSF to achieve target yield. Unlicensed use of Plerixafor has been reported in small case series with positive outcomes but there is limited long term data about safety and efficacy of Plerixafor in healthy donor. This retrospective analysis was performed to analyse the CD34 yields, failure to achieve >2x10⁶/kg CD34, failure to achieve requested target yield, apheresis parameters and predictors to achieve successful target yield in healthy related or unrelated donors.

Methods: From January 2017 to April 2024, 368 allogeneic donors underwent stem cell donation. Six donated twice and 374 individuals were included [M: 237, F:137; median age: 29 yr. (17-69); median donor weight: 82kg. (52-180); median patient weight: 79kg. (9-168); related: 84; unrelated: 290)]. Requested target dose was 2-4 (n=209), 5-7 (n=155) or >7 (n=10). Data was collected from apheresis data base, clinical records and hospital information system.

Results: 374 cases underwent 513 procedures. Median number of procedures was 1 (range:1-3) and 130 cases underwent more than 1 day harvest (34.8%). Median peripheral CD34 count on the day of harvest was 59 (7-246) and it was higher in unrelated donors (63 vs. 49, p= 0.0004), male donors (83.6 vs. 55.8, p=0.0001), donor weight>75 kg. (79 vs. 58, p= 0.001), donor age<40 (63 vs. 47, p=0.0002) but there was no relation to actual doe or banded dose of GCSF. CD34 yield showed linear correlation with peripheral CD34 (r=0.36, p=0.001).

Median CD34 yield was 5.1 (0-47.2). Only 11/374 (2.9%) cases had CD34 yield<2. Yield was lower in related donors (4.7; range: 0-8.9 vs. 5.9; range: 0.5-47.2; p=0.0001), female donors (M: 6.2, range: 0-47.2 vs. F: 4.7, range: 0-45.3; p=0.0001) and donor age above 40 yr. (4.8 vs. 5.6, p= 0.0002). Yield was lower in donors older than 40yr. (2.9 vs. 4.1, p=0.0001), donor weighed less than the patient (dL-rH: n=124, yield: 4.7, range:0.1-12.4 ; dH-rL: n=157, yield: 6.4, range: 0.0-47.2; same: n= 93, yield: 5.5, range: 0-14.1; p= 0.0001). Requested target dose was achieved in 260/374 (70%) cases. Incidence was higher but not significant with lower requested dose (2-4: n= 209, 73.2%; 5-7: n=155, 65.2%; >7: n=10, 60%; p= 0.21). Patient weight more than 10kg. from donor weight is associated with lower peripheral CD34 (48 vs. 63, p=0.0007), lower CD34 yield (4.1 vs. 5.7, p=0.0001) and higher incidence of failure to achieve target yield (48% vs. 24%, p= 0.001). Linear regression identified low peripheral CD34 count (p=0.001), older donor age (p=0.042), high recipient weight (p=0.001) and sibling donor (p=0.001) as predictors of lower CD34 yield and failure to achieve target yield.

Conclusions: Failure to achieve CD34 yield less than 2 is very small but 1 in 3 donors need more than 1 day harvest. Possibility to achieve requested CD34 yield in allogeneic donors is dependent on the requested CD34 dose, donor-patient weight difference, and type of donor (related or unrelated). Primary predictor is peripheral CD34 count and achieving adequate levels is dependent on the donor weight, age, gender and weight match with patient. This analysis supports the practice to choose younger male donors who are weight matched with the transplant patient.

Abdulgawad:Kite/Gilead: Honoraria. Castleton:AstraZeneca: Honoraria, Speakers Bureau; Amgen: Honoraria, Speakers Bureau; Pfizer: Speakers Bureau; Kite/Gilead: Honoraria, Speakers Bureau.