Donation Activities and Product Integrity in Unrelated Donor Allogeneic Hematopoietic Transplantation: Experience of the National Marrow Donor Program

Article Outline

• Abstract
• Introduction
• Methods
  • Study Population and Time Frame
• Results
  • Donor Activity
    • Single donations
    • Multiple donations
    • Product collected but not infused
    • Filgrastim injections administered but product not collected
    • Central line placement
    • Peripheral blood CD34+ cell mobilization and PBSC yields
  • Product Integrity
    • Positive product culture results in PBSC grafts
    • Positive culture reports in bone marrow products
    • Product clotting
    • Compromised product bags
    • Nonstandard product transport
• Summary
• Acknowledgements
• Copyright

Abstract 

Despite many clinical advances in allogeneic hematopoietic cell transplantation (HCT), the one factor that is consistently required to apply HCT to a wide variety of diseases is the successful donation and the safe transport and administration of viable donor cells to the HCT recipient. Since 1987, the National Marrow Donor Program (NMDP) has maintained a registry of volunteer HCT donors for those patients who lack a suitable related donor, facilitated the donor search, and managed the collection and transportation of donor cells to transplant centers for use in increasingly complex therapies. The NMDP has collected data on marrow and peripheral blood stem cell (PBSC) donations as well as additional donations of lymphocytes, whole blood, or platelets. These additional donations are provided for a variety of reasons, including treating post-transplant complications such as graft failure or relapsed disease, supporting immune reconstitution or providing transfusion support. For donor safety, rates of placement of central venous catheters for collecting PBSC are monitored. Data have also been collected on rare events that may affect the integrity of the HCT product (e.g., graft clotting or leaks from the transport bag). Quality assurance and review of these donation processes is an essential component of the transplantation approach. Data from the broad NMDP experience further illuminate factors surrounding the donation process and product integrity.

Key Words: National Marrow Donor Program, NMDP, Unrelated donor, Stem cell, Transplantation

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Introduction 

Allogeneic hematopoietic cell transplantation (HCT) has become a widely applied therapy for both hematologic and non-hematologic, malignant and non-malignant diseases. Since 1987, the National Marrow Donor Program (NMDP) has facilitated the identification, donation, and delivery of cells from a suitably matched, unrelated donor to patients who lack an appropriate related donor. With more sophisticated transplantation approaches, supportive care, and procedures for HLA-matching, the use of cells from NMDP donors has been applied to an increasingly diverse and growing population of patients. The provision of the HCT graft by the donor is an essential component of the HCT, yet few large databases are available to describe the experiences of an individual donor and the characteristics of the HCT product.

We describe the activities of NMDP donors, including those involving multiple marrow or peripheral blood stem cell (PBSC) donations as well as the donation of additional blood products for immune reconstitution, transfusion support, or treatment of post-transplant complications. Also described are the events that may have an impact on the integrity of the HCT product such as bag breakage or visual clumping or clotting of the product.

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Methods 

Study Population and Time Frame 

This report summarizes the donation activities of bone marrow donors from 1987 through 2007, and of PBSC donors from 1994 through 2007. Donation activity and CD34⁺ cell counts/PBSC yields were obtained from standard reports for each donation. Since 1987, the NMDP has required that all transplant centers perform microbial culture testing on each HCT graft.

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Results 

Donor Activity 

The majority of NMDP donors donated a single HCT product for one recipient. A total of 25,336 unique donors made 26,878 donations from 1987 through 2007. Of these 25,336 donors, 23,859 (94%) made a single HCT donation. An additional 1477 donors donated more than one HCT product, either for the same recipient or for more than one recipient.

Between 1987 and 2007, of the 25,336 NMDP donors who have donated, 870 (3.4%) donated more than one HCT product to a single recipient, including 857 who donated 2 times and 13 who donated 3 times (Table 1). Among those donors who donated twice for the same recipient, the majority initially donated bone marrow and then PBSC (51%), whereas approximately equal numbers of donors provided bone marrow (23%) or PBSC (22%) for both the first and second HCT donation. Only 3% of donors initially donated PBSC followed later by bone marrow.

Table 1. Donations by Cell Source from Donors Providing Multiple HCT Grafts to a Single Recipient

HCT indicates hematopoietic cell transplantation; PBSC, peripheral blood stem cell.

In contrast, 626 (2.5%) donors provided an HCT product to more than one recipient; 602 donated HCT for 2 different recipients, 23 donated HCT to 3 different recipients, whereas one donated bone marrow to 4 different HCT recipients (Table 2). Among the 602 recipients who donated for 2 different recipients, the majority of donors donated bone marrow for both recipients (53%). Less commonly, donors donated bone marrow for the first recipient and PBSC for the second recipient (27%), or PBSC for 2 recipients (12%). Only 4% of multiple donations consisted of PBSC for the first recipient and then bone marrow for the second recipient.

Table 2. Donations by Cell Source from Donors Providing HCT Grafts to More than One Recipient

HCT indicates hematopoietic cell transplantation; PBSC, peripheral blood stem cell.

Of the 1300 subsequent (second, third, fourth) HCT, 1241 (95%) were second HCT, 57 were third HCT, and 2 were fourth HCT (Table 3). As shown in Figure 1, whereas the absolute number of subsequent transplants has increased over time, since 1994 the percentage of subsequent HCT has remained between 3% and 6% of all transplants. Second transplants were performed for graft failure or delayed engraftment (46%) and relapse (34%), compared with graft failure (47%) and relapse (25%) for those undergoing a third transplant (Table 3).

Table 3. Reasons for Undergoing Second, Third, and Fourth Transplants

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• Figure 1. 

  Number of subsequent (second, third, fourth) NMDP-facilitated transplants, by transplant year.

Donors also provided additional blood products to support the transplant and later complications (Table 4). Unstimulated leukocytes for use in supporting immune reconstitution or treating relapse or graft failure were collected most frequently (82%). Whole blood and blood tubes were the next most frequently collected product. Platelets were donated only rarely, and no platelet collections have been documented since 2002.

Table 4. Additional Blood Products Collected for NMDP Transplant Recipients

From 1993 to 2007, there were 1402 additional blood products collected from 1316 donors to support a total of 1315 recipients.

Although rare, there were occasionally times when a donated product was not infused in the recipient. This was almost always because of the declining physical condition of the recipient. Of the 16,641 donations for a first NMDP bone marrow transplant from 1987 through 2007, there were 59 (0.4%) donated products that were not infused. Of the 9068 donations for a first NMDP PBSC transplant from 1997 through 2007, there were 47 (0.5%) donated products that were not infused. For the same time periods, the percentages of bone marrow and PBSC products collected but not infused were 1.2% (5 of 406) and 1.6% (14 of 855) for subsequent (second, third, or fourth) bone marrow and PBSC transplants, respectively.

Of the 9995 donors who received filgrastim injections from 1994 through 2007, 72 (0.7%) received at least 1 injection of filgrastim but did not have PBSC collected. The cancelled collections were almost always because of the declining physical condition of the recipient.

The NMDP protocol for collection of PBSC allows for central venous lines to be placed in the donor if blood flow from the standard peripheral venous line is not adequate. The site of central line placement in male and female donors is detailed in Figure 2, whereas the frequency of line placement over time in male and female donors is shown in Figure 3. For donors undergoing a 1-day collection, the frequency of internal jugular and femoral line placement was similar, with both the internal jugular and femoral locations utilized twice as often as the subclavian vein. In contrast, the femoral location was utilized much less frequently for donors scheduled to undergo a 2-day collection. Since the year 2000, the frequency of line placement has remained relatively stable at approximately 2% to 5% in male donors and 18% to 24% in female donors. Over the time period of data collection, the proportion of collections with central lines was significantly greater for 1-day (624 of 4477 collections, 14%) versus 2-day collections (201 of 3387 collections, 6%, P < .001).

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• Figure 2. 

  Placement of central lines according to anatomic location for donors undergoing 1-day and 2-day PBSC collections in male and female donors. For donors scheduled for a 1-day collection, the frequency of central line placement was similar in the internal jugular and femoral locations, each of which occurred more than twice as frequently as placement in subclavian or other locations. In contrast, the frequency of femoral line placement was less common, whereas the frequency of internal jugular and subclavian vein placement was more common in donors scheduled to undergo a 2-day collection.

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• Figure 3. 

  Frequency of male and female donors receiving central venous catheter placement, by year of collection. The rate of line placement has remained stable since the year 2000 for both male and female donors, at between 18% and 24% for females, and between 2% and 5% for males.

Figure 4 shows the day 5 peripheral blood CD34⁺ cell count following filgrastim administration but prior to PBSC collection. For all donors, filgrastim was administered at a targeted dose of 10 to 12 μg/kg of body weight subcutaneously for 5 consecutive days. As shown in Figure 5, the actual PBSC yield following apheresis was highly correlated with the peripheral blood CD34⁺ cell count, indicating the high predictive impact of this parameter on the overall CD34⁺ cell content of the graft. For both men and women, the post-filgrastim CD34⁺ cell counts prior to apheresis increased with increasing donor weight, and thus with increased total filgrastim administered. CD34⁺ cell counts were similar in men and women who weighed between 80 and 120 kg, whereas women at lower body weights had somewhat lower CD34⁺ cell counts than men at lower body weights.

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• Figure 4. 

  Peripheral blood CD34⁺ cell counts in female and male donors following administration of filgrastim subcutaneously for 5 days at a targeted dose of 10 to 12 μg/kg/day. In both female and male donors, the CD34⁺ cell count increased with increasing donor weight (higher total amounts of filgrastim). Higher responses were also observed in male compared to female donors with body weights of <80 kg.

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• Figure 5. 

  Apheresis PBSC collection efficiency, plotted as the CD34⁺ cell yield per liter, processed versus the CD34⁺ cell concentration in peripheral blood at the beginning of apheresis. The product yield was highly correlated with the pre-apheresis CD34⁺ cell count. The collection efficiency was 38%, indicating that the product yield increased by 0.38 × 10⁶/L processed for every 1 × 10⁶ cell/L increase in the pre-apheresis CD34⁺ concentration.

Data in Figure 5 were used to calculate the efficiency of PBSC collection by apheresis, (CD34⁺ cells in the apheresis product per liter of whole blood processed divided by the CD34⁺ cell concentration in the peripheral blood). For the nearly 3000 collections, the mean collection efficiency was 38% (95% confidence interval 37-38). Ten of 101 (10%) collection centers (mean of 28 collections per center) had mean collection efficiency values with an upper 95% confidence limit that was 10% or more below this overall mean value (i.e., less than a mean efficiency of 34%).

Product Integrity 

A positive product microbiologic culture was reported in 29 PBSC grafts. Other than infusion reactions, no long-term effects of bacteremia and no deaths attributable to sepsis were reported. In 5 instances the recipient developed fever, chills, nausea, hypotension, or other complications consistent with infection; in 1 instance hemolysis from incompatible plasma may have contributed to the clinical event. In 19 of the 29 events, the positive culture was reported by the apheresis center. Of these 19 events, 18 were confirmed negative by testing at the transplant center, and 1 was not tested at the transplant center. In the remaining 10 events, the transplant center reported a positive result with testing either not done or results not available at the apheresis center. In 21 of the 29 events where data on antibiotic therapy was available, 10 recipients were already receiving prophylactic antibiotic therapy, 9 received antibiotic therapy upon receipt of the bacteriologic report, and 2 were not started on antibiotic therapy as testing at the transplant center was negative. Of the 28 recipients for whom engraftment data was available, engraftment was reported in 26 of the 28 recipients who received a possibly contaminated product. Organisms identified included Staphyloccocus species (13), propionobacteria, diptheroids, and gram-variable rods (5), gram-positive cocci (4), Salmonella (2), Bacillus species (2), fungus (2), Pseudomonas species (1), Gram negative (1), and others (4).

Positive cultures were reported in 145 bone marrow products. Of these 145 events, 69 were reported positive by the transplant center. Of the remaining 76 events reported positive by the collection center, 68 were confirmed negative by the transplant center and 8 were not tested at the transplant center. No deaths were attributed to infusion of these products. In 13 recipients, unexpected symptoms including fever, hypotension, hypertension, nausea, changes in heart rate, or hypoxia were reported. In 78 cases the recipient was already receiving prophylactic antibiotic therapy at the time of the positive culture report; 38 recipients were placed on antibiotic therapy following the positive culture report. Of the 129 recipients for whom engraftment status was known, engraftment was reported in 118. A total of 172 positive culture reports identified Staphylococcus species in 57 products, propionobacteria, diptheroids, corynebacteria, and gram-positive or gram-variable rods in 47 products, gram-positive cocci in 37 products, peptostreptococcus in 6 products, Micrococcus species in 7 products, fungus or mold species in 8 products, Clostridia species in 2 products, and 8 others.

Product clotting was reported in only 5 PBSC and 5 marrow products. For the 5 PBSC products, no unexpected adverse events were reported. One of the PBSC products was filtered, 3 had additional anti-coagulant added, 1 had no specific intervention made, and 1 was infused via syringe with visual inspection. A median infused cell dose of 6 × 10⁶ CD34⁺ cells/kg recipient weight was reported and engraftment occurred in 4 of 4 recipients with available data. In the 5 bone marrow products, 1 adverse event was noted when a recipient complained of dyspnea 1 hour after infusion, with resolution 1 hour later. Two of the bone marrow products were filtered, 2 were filtered and had additional anti-coagulant added, 1 had no additional intervention made. The median infused nucleated cell dose was 1.2 × 10⁸/kg and only 1 of 3 products with available data engrafted.

Three PBSC products had bag leaks and breakage reported upon receipt by the transplant center. Culture results were negative in all 3 cases. One was infused using prophylactic antibiotics, 1 was transferred to another bag, and 1 case had no specific intervention. Engraftment occurred in all 3 recipients. Four bone marrow products were reported to have bag leaks and breakage; 3 were reported by the transplant center, and 1 by the collection center. Culture results were negative in all 4 cases. Two were infused after transfer to another product bag, and 2 had no specific intervention. Engraftment occurred in all 4 cases.

NMDP standards for product transport indicate that the product must be maintained within a specified temperature range and must not be subject to airport x-ray examination. During this period, 10 PBSC products were identified as having undergone incorrect transport; 4 were x-rayed during transport and 6 arrived at incorrect temperature. All 10 products were infused without specific intervention and engraftment was reported in all 10. Four bone marrow products were identified by the transplant center as having undergone incorrect transport; 1 was x-rayed and 3 arrived at incorrect temperature. All 4 were infused without specific intervention; engraftment was reported in 2 of 2 recipients with available data.

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Summary 

The data reported herein indicate that NMDP network transplant recipients may receive a second or more unrelated HCT graft primarily as a therapy for relapsed disease or graft failure, and that altruistic, volunteer donors may at times provide a second, third, or, very rarely, a fourth donation of HCT cells to the same or to a different recipient. Also, donors not infrequently provide additional blood products to promote improved recipient outcomes. The majority of these products are unstimulated mononuclear cell apheresis products for immunotherapy of graft failure or relapse.

The donation process for PBSC involves administration of filgrastim to increase circulating levels of CD34⁺ cells in blood, and may require placement of indwelling central venous catheters. The collection of PBSC also involves expertise in assessing the choice of peripheral venous access versus central line placement, and operation of sophisticated apheresis devices for collection of the donor PBSC graft. The degree of mobilization of the donor CD34⁺ cells and the efficiency of CD34⁺ cell collection may substantially affect the quantity of cells in the PBSC graft. This may be an important consideration for engraftment, especially in larger weight recipients and in transplant approaches utilizing complex cell processing therapies. Absent widely and readily available data for performance standards and outcome data regarding this process, this information may be used to track and improve these elements that have an impact on both donors and recipients.

Product integrity may rarely be compromised, primarily by positive microbial product cultures, but also by rarer events involving apparent clotting of the product, breaks, or leaks in the product bags. Errors can occur during the transport process. Although systematic procedures to follow-up on all these events were incomplete, in general, these uncommon product integrity compromise events had little impact on the recipients' outcome. Only in a few cases of clotted marrow products was there an association with graft failure, but the rarity of the cases reinforces confidence that the network procedures, when followed, provide a safe and satisfactory graft product for almost every recipient.

Through additional internal review, analysis, and dissemination of corrective procedures within the NMDP network of centers, examination of these events may improve science, understanding, and processes to enhance the donor and recipient safety as transplantation of hematopoietic products continues to expand.

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Acknowledgements 

Financial Disclosure: Drs. J. Miller, R. Miller, Hanley, Chitphakdithai, and King are employees of the NMDP and have a financial relationship with the NMDP, in that capacity as employees. Drs. Bolan, Hartzman, Perry, and Trainor have nothing to disclose.