An Assessment of the Outcomes of Second Donation Requests through the Canadian Blood Services Onematch Unrelated Registry

Introduction:  Allogeneic transplants using hematopoietic stem cells from unrelated donors (alloHSCT) have become more common than related transplants. Matched unrelated alloHSCT in Canada are facilitated by the OneMatch Stem Cell and Marrow Network. Patients may undergo a second unrelated alloHSCT with prior conditioning or simply receive an infusion of cells from an unrelated donor [donor lymphocyte infusion (DLI)]. There have been few studies examining the outcomes of second unrelated alloHSCT or DLI in large numbers of patients and none involving the Canadian registry. 

Methods:  We examined a consecutive series of Canadian patients who received a second unrelated alloHSCT or DLI through OneMatch during the period between January 1^st 2002 and December 31^st 2011. We collected information about disease type and status at the time of first transplant, first transplant date, indication for and date of second transplant or DLI, and the graft types (bone marrow, G-CSF stimulated peripheral blood or unstimulated DLI) and conditioning regimens for both transplants. Survival status, disease status, and engraftment status at most recent follow-up were also collected. Donor and recipient information including year of birth and weight was also collected. 

Results:  There were 128 consecutive Canadian patients who received a second unrelated alloHSCT or DLI during the period specified. Median age of recipients was 37 (range:  2-68).  There were 73 males, 36 females, and 19 patients whose sex was unknown. The most common indication for second transplant or DLI was disease relapse (n=68, 53%), followed by graft failure (n=37, 29%).  The most common disease for which the first transplant was undertaken was acute myeloid leukemia (n=37, 29%), followed by lymphoproliferative disorders (n=29, 23%). The most common graft type for second transplant was unstimulated peripheral blood (65, 51%), and 101 of 128 (79%) second transplants used the same donor as for the first transplant. Median survival was 1.03 years (95% CI = 0.87-1.69). Median time between transplants was 10.56 months (0.6-105.72). Patients whose time between transplants was above the median were more likely to be alive at last follow-up, (p=0.029) and they exhibited higher survival in the first year post-transplant. No other factors were found to significantly affect survival. 

This study is the first to examine a consecutive series of unselected patients receiving a second donation of hematopoietic stem cells from an unrelated donor using the Canadian registry. Survival is comparable to previous studies using the American (Schriber et al., 2010) and German (Platzbecker et al., 2008) registries. This study shows that outcomes do not differ significantly based on disease, age, gender, conditioning regimen, and graft type. Further studies will be needed to identify factors that better predict outcomes when utilizing this scarce resource.