Availability of HLA-allele-matched unrelated donors and registry size: Estimation from haplotype frequency in the Italian population.

In Italy, an HLA-matched unrelated donor is currently the primary donor when a HLA matched sibling is not found for allogeneic haematopoietic stem cell transplantation (HSCT). Better outcomes for transplantation require optimal matching between donor and recipient at least at the HLA-A, -B, -C, and -DRB1 loci; therefore, the availability of HLA-matched unrelated donors is important. The enormous HLA polymorphism has always necessitated registries with a large number of individuals in order to be able to provide well-matched donors to a substantial percentage of patients. In order to increase the efficiency of the Italian Bone Marrow Donor Registry (IBMDR) in providing Italian patients with a suitable donor, the probability of finding an HLA-A, -B, -C, and -DRB1 allele-matched (8/8) or a single mismatch unrelated donor (7/8) was estimated in this study according to IBMDR size. Using a biostatistical approach based on HLA haplotype frequencies of more than 100,000 Italian donors enrolled in the IBMDR and HLA-typed at high-resolution level, the probability of finding an 8/8 HLA-matched donor was 23.8%; 33.4%; and 41.4% in simulated registry sizes of 200,000; 500,000; and 1,000,000 donors; respectively. More than 2 million recruited donors are needed to increase the likelihood of identifying an HLA 8/8 matched donor for 50% of Italian patients. If one single mismatch at HLA I class loci was accepted, the probability of finding a 7/8 HLA-matched donor was 62.8%; 73.7%; and 80.3% in 200,000 donors; 500,000; and 1,000,000 donors; respectively. Using the regional haplotype frequencies of IBMDR donors, the probability of recruiting a donor with a new HLA phenotype, in the different Italian regions, was also calculated. Our findings are highly relevant in estimating the optimal size of the national registry, in planning a cost-effective strategy for donor recruitment in Italy, and determining the regional priority setting of recruitment activity in order to increase the phenotypic variability of IBMDR as well as its efficiency.

Outcome of patients activating an unrelated donor search: the impact of transplant with reduced intensity conditioning in a large cohort of consecutive high-risk patients.

An unrelated donor (UD) search was submitted to the Italian Bone Marrow Donor Registry between February 2002 and December 2004, for 326 consecutive patients with hematological malignancies, eligible for a reduced intensity conditioning (RIC) UD transplant. Only two regimens were allowed: melphalan, alemtuzumab, fludarabine and total body irradiation of 200 cGy (regimen A) and thiotepa, cyclophosphamide, anti-thymocyte globulin (regimen B). The outcome of patients receiving an UD transplant (n=121) was compared with patients who did not find a donor (n=205), in a time dependent analysis, correcting for time to transplant. The median follow up from activation of donor search was 6.1 years. UD transplant was associated with a significantly better survival in patients with acute leukemia and non-Hodgkin's lymphoma (NHL) whereas only a favorable trend was documented for Hodgkin's disease. No survival benefit was registered for chronic leukemias. The outcome of the two different conditioning regimens was comparable, in terms of survival, transplant-related mortality and graft versus host disease. In conclusion, finding an UD and undergoing a RIC transplant significantly improves survival of patients with acute leukemia and NHL. The advantage is less clear for HD and chronic leukemias. The role of different conditioning regimens remains to be elucidated by prospective clinical trials.

Donor safety: the role of the WMDA in ensuring the safety of volunteer unrelated donors: clinical and ethical considerations.

Since the beginning of hematopoietic stem cell harvesting from volunteer unrelated donors, ensuring donor safety has been a necessary goal of all parties involved in the process. As donation of BM or PBSCs is not in the interest of the donor's own physical health, donor registries and transplantation centers must take into account both medical and ethical aspects involved in the donation procedure. One of the principal goals leading to the formation of the World Marrow Donor Association (WMDA) was to establish internationally acceptable standards for all aspects of unrelated donor care.

HLA matching affects clinical outcome of adult patients undergoing haematopoietic SCT from unrelated donors: a study from the Gruppo Italiano Trapianto di Midollo Osseo and Italian Bone Marrow Donor Registry.

The importance of HLA donor-recipient matching in unrelated haematopoietic SCT (HSCT) is the subject of debate. In this retrospective study, we analyzed 805 adult patients from the Italian Registry receiving HSCT for a haematological malignancy from January 1999 to June 2006 and correlated the degree of HLA matching with transplant outcome. All patient-donor pairs had high-resolution typing at HLA-A, -B, -C, -DRB1 and -DQB1. There was a significantly higher risk of overall mortality, non-relapse mortality, graft failure and acute GVHD (aGVHD) for patients receiving HSCT from an unrelated donor with one or more low- or high-resolution mismatch/es (Mm/s). When only a single HLA Mm is present (9/10 matched pairs), mortality risk is higher than among 10/10 matched pairs in patients transplanted with acute leukaemia in the first CR ('early' patients) but not in the other patients (advanced patients): HR=1.69, 95% CI=0.94-3.02, P=0.08; HR=1.03, 95% CI=0.80-1.32, P=0.82, for early and advanced patients, respectively. These results confirm that the advantage of a 10/10 match has a greater effect in early patients, thus suggesting that a 9/10 matched donor can be chosen in patients with advanced disease lacking a rapidly available 10/10 matched one.