Second Unrelated Donor (URD) Transplant as a Rescue Strategy for 122 Patients with Primary Non Engraftment: Results from the CIBMTR
Authors: Schriber Jeffrey R. , Agovi Manza- A , Ballen Karen K , Bacigalupo Andrea , Hale Gregory A. , Gupta Vikas , Lazarus Hillard M. , Litzow Mark R. , Marks David I. , Giller Roger H. , Maziarz Richard T. , Bornhauser Martin , Isola Luis M. , Bredeson Christopher , Rizzo J. Douglas 
Published: October 2019

Few data are available on the outcomes of patients who fail to engraft following URD transplantation. We describe the results of 122 patients reported to the National Marrow Donor Program (NMDP) between 1990 and 2005, who received a second bone marrow (BM) or peripheral blood (PB) URD transplant after failing to achieve an absolute neutrophil count of ≥ 500/mm3 without evidence of recurrent disease. Patients were transplanted for leukemia (n=83), myelodysplastic disorders (n=16), severe aplastic anemia (n=20) and other disease (n=3). The median age at first transplant was 29 years. Approximately one third were in each age range, < 20 (33%), 20–40 (37%) and >40 (29%). The initial transplant was BM in 84% of patients while 51% received BM for the subsequent transplant. One hundred ten of these patients received two transplants, 11 received three and one received 4 transplants. Twenty four used a different donor whereas 98 used the original donor for the second transplant; 28 of these used cells that had been cryopreserved at the initial transplant date. Nearly two thirds of the patients received reduced intensity conditioning or no conditioning for the second transplant. Sixty one percent had ATG as a component of their second transplant. The median interval from first transplant to second transplant was 48 (range, 18–126) days. The median nucleated cell dose was 2 × 108/kg (range, <1–23) for the first transplant and 2 × 108/kg (range, <1–50) for the second. The median follow up of survivors after second transplant was 77 (range, 2–144) months. Univariate probabilities of outcomes for these patients after second transplant were:

Outcome N eval Probability (95% CI) *cumulative incidence Neutrophil engraftment* 122 @ 28 days 43 (34–52) % @100 days 48 (39–57) % 30 day mortality 122 39 (31–48) % 100 day mortality 122 75 (67–82) % Overall survival (OS) @ 1 year 122 11 (6–17) % Treatment related mortality (TRM) @ 1 year* 99 86 (79–92) % Disease free survival (DFS) @ 1 year 99 7 (2–12) %

Of the 122 patients analyzed, only 10 remain alive. The most common causes of death were graft failure or rejection (33%), organ failure/interstitial pnuemoniatis (22%), infection (15%), GVHD (14%) and recurrent disease (6%). Of the 37 patients who had persistent graft failure 21 (57%) died from infectious causes.

We observed no differences between patients who received a graft from the same donor vs. different donor, fresh vs. cryopreserved cells, or small initial graft size vs. large initial graft size. Patients who received a T-cell depleted graft at the time of their first transplant had significantly worse survival at 1 year after their second transplant, 4% (95% CI, 0–11) compared to those patients who had a non T-cell depleted initial graft, 16% (95 % CI, 8–25)(P = 0.02). It appears that a second salvage transplant strategy may be effective in a small group of patients, although the overall DFS at 1 year of only 7% is disappointing. To improve these results, efforts might focus on early identification and treatment of those at highest risk for non engraftment to determine whether such a strategy can alter the natural history we have described.