Prognostic Factors for the Engraftment in Cord Blood Transplantation: With Units Shipped from Single Cord Blood Bank, Tokyo Cord Blood Bank.

The better selection of cord blood (CB) unit in recent varied cord blood transplantation (CBT) is crucial for the success of CBT, although it is difficult to compare the units from different cord blood bank (CBB). Here, we analyzed the prognostic factors by age for engrafment in CBT with the units shipped from single CBB, Tokyo Cord blood bank.

Patients and Methods: Units were all processed by HES centrifugation method and cryopreserved with 10% DMSO and Dextran 40 in Tokyo CBB. CD34 was analyzed by gating CD45dim CD34+ with DNA dye or 7-AAD in Trucount beads tube (BD). Patients characteristics are shown in table. Group I included 58u for malignancies and 25 for non-malignancies. Group III included 22 full(Full) vs.22 reduced intensity (RI) conditioniong regimen for malignancies and remaining ones with further reduced intensity regimens. RI regimen consisted maily with reduced dose of TBI (<8Gy) and BU/Melphalan with fludarabin.

Results: Myeloid engraftment in malignancies with Full regimen was seen at 84.3%(median 28days) in Group I, 82.5%(25days) in Group II and 73.0%(30days) in Group III, respectively, whereas with RI regimen in Group III was 67.8%(24days). The patients with non-malignancies in Group I showed 75.0% (26days) of engraftment by Full regimen(n=12) and 100% (24days) by RI regimen(n=8), respectively. HLA disparities had no significant influence on the engraftment in Group I and II. The dose effects of NC and CD34⁺ cells on the rate and the speed of engraftment were seen in Full regimen in Group I and II for malignancies. Critical dose of CD34⁺ cells seemed 0.8x10⁵/kg. Even in Group I(children), the patient with CD34⁺ less than 0.8x10⁵/kg showed 79.6%(43days), whereas those with more than 0.8x10⁵/kg, 85.7%(24days). There was no difference of speed and rate of engraftment between the patients with CD34⁺ cells 0.8~1.6x10⁵/kg and those with more than 1.6x10⁵/kg. Interestingly, this effect vividly influenced on the engraftment in the patients with RI regimen of Group III. The patients with CD34 ⁺ with less than 0.8x10⁵/kg showed only 22.9% of final engraftment, whereas those with over 0.8x10⁵/kg 100% (19 days) in Group III. The dose of CD34⁺ had some influeced on the survivals, although the main prognostic factors on the long-term survivals was the risk factor of malignancy and age.

Conclusion: CD34⁺ cell dose should be given high priority for the selection of CB unit, especially in reduced intensity regimen.