Cryopreserved, banked CB is being increasingly used for allogeneic bone marrow reconstitution of unrelated transplant recipients. The effect of long-term storage on the viability and function of CB hematopoietic stem cells has been addressed only with in vitro assays and immunodeficient mouse models (

Broxmeyer et al,
), but not in clinical transplantation. To evaluate the quality of CB units after prolonged storage in liquid nitrogen freezers, we compared the transplantation outcomes of patients that received CB grafts from the New York Blood Center NCBP stored for 8 years or more (Group 1, N=43, median time from unit collection to transplant: 9.2 years) to those transplanted with units stored < 2 years (Group 2, N=300, median time: 1.1 years). Patients were included in the study if they were transplanted in the period 2001–2006, received a single or double unexpanded unit graft and had no prior transplant in the 6 months preceding the CB graft. Double unit recipients were evaluated if the unit of interest was the one that engrafted, as demonstrated by post-transplant chimerism studies. The two groups were similar with respect to disease category (malignant diseases: 74% in Group 1, 69% in Group 2), location of transplant center (transplant in the US: 60% and 68%, respectively), use of non-myeloablative regimens (19% and 12%, respectively) and double unit transplants (14% and 10%, respectively). More patients in Group 1 were adults (42% and 27%, respectively, p = 0.035). Detailed information on CB thawing was available for all units in Group 1 and 217 in Group 2. Two units of the first Group and 3 of the second were reported to have problems at thawing (clots/leak). No immediate post-infusion complications were reported. Post-transplant ANC recovery was at a median of 25 days in Group 1 and 22 days in Group 2 (multivariate RR = 0.9, p = 0.6). Among patients who survived for 28 days or longer, 8/36 in Group 1 and 42/260 in Group 2 failed to achieve ANC500 (p = 0.3). Overall survival was not different in the two Groups (both 49% at 5 years). These results indicate that “old” CB units can be used effectively in clinical transplantation. Therefore, long-term cryopreservation of CB stem cells is feasible without compromising the quality and engraftment ability of the CB units, supporting the creation of a National Cord Blood Inventory with high quality units. However, these findings need to be viewed with caution: cryopreservation and storage procedures, equipment and devices vary significantly among different Banks. Thus, the results of the NCBP may not apply to all Cord Blood Banks.

Author notes

Disclosure: No relevant conflicts of interest to declare.