Long-term risks of hematological malignancy, autoimmune or thrombotic events do not differ in bone marrow and filgrastim-mobilized PBSC donors

Background 

Research presented at the 64th American Society of Hematology (ASH) Annual Meeting and Exposition showed that peripheral blood stem cell (PBSC) donors receiving filgrastim were not at an increased risk of malignancy, autoimmune or thrombotic events (MAT) compared to unstimulated bone marrow (BM) donors who didn’t receive filgrastim.   

NMDP is committed to connecting hematopoietic stem cell donors to patients in need of allogeneic hematopoietic cell transplantation (HCT) through the national registry while ensuring donor safety. Hematopoietic stem cells are collected from adult donors through unstimulated BM harvest or filgrastim-mobilized PBSC collection.

Filgrastim is a medication often used to mobilize PBSC and is given to donors via daily subcutaneous injection for 5 days. Historically, data collected on donors has focused on short-term donor adverse events (AEs) following both unstimulated BM and filgrastim-mobilized PBSC collection, but long-term AE data are limited. 

Study Details 

This study consisted of both a retrospective cohort and a prospective cohort. The retrospective cohort included donors who underwent a BM or PBSC collection between July 1, 1999, and Sept. 30, 2010. The prospective cohort included donors who underwent a collection after study activation on Oct.1, 2010.

Donors consented to a biennial phone survey to report MAT events until the study’s completion. Accrual closed on Sept. 30, 2015, and follow-up phone surveys were completed on Sept. 30, 2020. The final cohort included 21,653 donors. The median time to the last survey completion was 7 years (range 0.6-20.2) for PBSC donors and 9 years (range 0-29.2) for BM donors. 

Results 

Almost double the donors were exposed to filgrastim (14,530 PBSC) than those who were not (7,123 BM donors). Results showed that the incidence of MAT events in filgrastim-mobilized unrelated PBSC donors compared to unstimulated BM donors was not significantly different. Incidence rates are available in Table 1 below.

This study suggests that donors who receive filgrastim are not at a higher risk of MAT events.  

Key Takeaways 

This study is the largest and most comprehensive regarding the long-term effects of filgrastim in unrelated PBSC donor outcomes related to MAT disorders. Results show that donors who receive filgrastim are likely not at an increased risk of MAT events compared to BM donors who didn’t receive it.

A low risk of MAT events can provide reassurance to donors undergoing stem cell mobilization and those considering becoming donors through stem cell registries such as the NMDP^SM.   

Table 1. Incidence rates of MAT events  

Stefanski HE, et al., ASH poster presentation abstract