EXTENDED ABSTRACT
Background:
Approximately 7% of unrelated hematopoietic stem cell donors are asked to donate stem cells a subsequent time to the same or different recipient. Recent studies have shown that donation related symptoms for second donations were similar to the first donation experiences. Little is known about differences in stem cell mobilization and yields for subsequent peripheral blood stem cell (PBSC) and bone marrow (BM) collections.
Objectives:
We hypothesized that CD34+ cell yields and total nucleated cell (TNC) concentrations for subsequent PBSC or BM donations are lower than those at the first donation. We also evaluated the factors influencing stem cell yields in healthy unrelated second time donors.
Study design:
Data were gathered from the Center for International Blood and Marrow Transplant Research (CIBMTR) database on 513 PBSC and 43 BM donors who donated a second. Time between 2006 and 2017 through the National Marrow Donor Program (NMDP).
Results:
Among second time PBSC donors, we found significantly lower pre-apheresis peripheral blood CD34+ cells counts (106/L) (68.6 vs. 73.9; p=0.03), and collection yields (x106) (556 vs. 608; p=0.02) at the second donation compared to the first. This decrease at the subsequent donation was associated with a shorter inter-donation interval, decrease in BMI, and a lower total G-CSF dose. In most instances, sub-optimal mobilizers at first donation donated suboptimal numbers of HSC at their subsequent donations. Among repeat BM donors, the TNC concentration was lower at the second donation. A low sample size in this group precluded additional analysis.
Conclusions:
Overall, when considering repeat donations, increasing inter-donation intervals and evaluating for BMI changes should be considered to optimize stem cell yields. Some of these parameters may be improved by increasing G-CSF dose in PBSC donors within permissible limits.
INTRODUCTION
Allogeneic stem cell transplantation is an important curative option in the management of many benign and malignant hematologic diseases. The success of the therapeutic modality is attributable, in part, to improved access to matched unrelated volunteer donors through donor registries. Annually, the National Marrow Donor Program (NMDP) registry facilitates more than 5,000 transplants using G-CSF mobilized peripheral blood stem cells (PBSC) or bone marrow (BM) as graft sources[1]. While most patients receive a single transplant, graft failure and disease relapse may prompt subsequent stem cell requests from donor centers. Between 5 and 10% of matched-related and -unrelated donors are asked for repeat donations[2], which include donor lymphocyte infusions and/or additional stem cell graft collections. Donors may also be asked to donate a second time for a different HLA-matched recipient.
The safety of second donations has been evaluated in people donating BM or PBSCs by apheresis following the administration of G-CSF. People donating BM twice were found to experience more symptoms and to recover more slowly than those donating G-CSF mobilized PBSC on two separate occasions overall (i.e. at first and second donation). The occurrence and severity of adverse events at second donation was similar to that in the first donation among individuals who underwent two PBSC or two BM collections [3, 4].
When deciding if a donor should be asked to donate again and if so, when to donate, it is important to know not only about the donor’s recovery from the prior donation, but also the quality of stem cells that such a donation would yield. It is known that some donor attributes influence the yield of first PBSC collections. CD34+ cell mobilization directly affects collection yields and donor attributes such as age, race, sex, Body Mass Index (BMI) and dose of G-CSF (filgrastim) impact stem cell mobilization [5]. Baseline hematologic parameters such as hematocrit, platelet counts, and absolute neutrophils also appear to influence yield of CD34+ cells in PBSC after G-CSF mobilization [6, 7]. Some of these factors may influence second donation yields as well. However, few studies have evaluated factors influencing CD34+ cell yields at subsequent PBSC donations and TNC cell yields in second BM donations. Previous studies have suggested that inter-donation intervals may impact second collections, but these studies could not be definitive due to limited donor numbers [3, 8–15] [16–19]. It may be useful to understand whether increasing G-CSF dose at the second mobilization could optimize yields in apheresis collections in donors who had poor yields with the first collection. The predictive role of donor demographics and laboratory parameters in CD34+ cell mobilization and collection yields at second donations also merits detailed assessment.
The purpose of this study is to identify factors influencing stem cell graft quality and yield at subsequent donations in donors undergoing collections via the same route (PBSC only or BM only) for all donations. The results will inform decisions on donor identification, optimal inter-donation interval and G-CSF dosing for re-mobilization.
METHODS
Study population:
NMDP donors of G-CSF mobilized PBSC or non-mobilized BM between 2006 and 2017, with a subsequent donation from the same stem cell source were included in the study. Donors donating at international apheresis centers, and donors missing essential forms, were excluded. In accordance with the Declaration of Helsinki, written informed consent was obtained from all donors for participation in Center for International Blood and Marrow Transplant Research (CIBMTR) studies, which were NMDP-sponsored and IRB-approved. Mobilized PBSC and BM collections were performed as previously described [3, 20].
Study outcomes and statistical analysis
Analyses evaluated the impact of inter-donation interval, donor demographics (age, BMI, race, sex, G-CSF dose, year of procedure, need for central line) and changes in complete blood counts (CBC), on the CD34+ cell yields/liter (x106/L) of blood processed at second donation and pre-apheresis (Day 5) peripheral blood CD34+ cell counts/liter (x106/L) at second donation. In the case of BM collections, the study evaluated effect of the same variables on the final TNC per liter of BM collected. CD34+ cell and TNC enumeration were performed per standard assessments.
Traditional linear regression was used to model log cell yields as a function of donor and collection related variables, time between donations, and changes in baseline values from first to second donation. Stepwise model building, along with interactions among significant variables were assessed. Comparisons between donation 1 and donation 2 characteristics and outcomes were done using paired tests (Wilcoxon signed rank test or McNemar’s test for continuous or categorical variables, respectively). “Optimal” or “sub-optimal” mobilizers were defined as those with Day 5, pre-apheresis CD34 counts (106/L) of ≥73.9 or <73.9, respectively (see explanation for this designation in the results section). For all analysis, a significance level of 0.01 was used. A p-value of 0.01–0.1 was considered to demonstrate a trend. No imputation of missing values was used; rather missing covariate categories were created for multivariate analysis, and complete case analysis was used for outcomes. SAS version 9.4 was used for analysis.
RESULTS
PBSC donor and collection characteristics
Data were available on 513 PBSC donors who donated a second PBSC product (Table 1). A majority of the second time PBSC donors were Caucasian (74%), male (72%), aged 18 to 29 years at first (49%) and second (41%) donations. The median weight of donors did not differ significantly between first and second PBSC donations (83kg vs. 84kg; p=0.25). A majority of the PBSC donors demonstrated BMIs in the range of 18.5–29.9 at first (71%) and subsequent (68%) donations. At baseline, i.e. prior to each PBSC mobilization, no clinically relevant differences were notable between the 2 donations in the WBC, hematocrit, platelet or mononuclear cell counts.
Table 1.
Demographic characteristics for two-time domestic PBSC donors with a first donation between 2006 and 2017
| 1st donation | 2nd donation | ||
|---|---|---|---|
| Variable | N (%) | N (%) | p-value |
| Number of donors | 513 | 513 | |
| Number of centers | 86 | 75 | |
| Sex | |||
| Female | 142 (28) | 142 (28) | |
| Male | 371 (72) | 371 (72) | |
| Donor age at donation | <0.001 | ||
| 18 to 29 | 251 (49) | 211 (41) | |
| 30 to 39 | 113 (22) | 139 (27) | |
| 40 to 49 | 91 (18) | 92 (18) | |
| 50+ | 58 (11) | 71 (14) | |
| Median (Range) | 31 (18–61) | 33 (19–61) | <0.001 |
| Race | |||
| Caucasian | 379 (74) | 379 (74) | |
| Hispanic | 44 (9) | 44 (9) | |
| Black/African American | 24 (5) | 24 (5) | |
| Asian/Pacific Islander | 18 (4) | 18 (4) | |
| American Indian/Alaska Native | 6 (1) | 6 (1) | |
| Other/Multiple Race | 34 (7) | 34 (7) | |
| Decline/Unknown | 8 (2) | 8 (2) | |
| Weight at baseline (kg) | |||
| N Eval | 513 | 513 | |
| Median (Range) | 83 (43–144) | 84 (45–148) | <0.001 |
| Body Mass Index (BMI), kg/m2 | 0.008 | ||
| Underweight (<18.5) | 3 (1) | 0 | |
| Normal (18.5–24.9) | 176 (34) | 164 (32) | |
| Overweight (25–29.9) | 191 (37) | 182 (36) | |
| Obese (30+) | 142 (28) | 165 (32) | |
| Unknown | 1 (N/A) | 2 (N/A) | |
| Requested CD34+ cell count (x106) | |||
| N Eval | 225 | 218 | |
| Median (Range) | 435 (120–1261) | 450 (55–1275) | 0.621 |
| Baseline WBC (x109/L) | |||
| N Eval | 513 | 512 | |
| Median (Range) | 6.1 (2.9–13.9) | 5.9 (2.7–11.5) | <0.001 |
| Baseline hematocrit (%) | |||
| N Eval | 513 | 512 | |
| Median (Range) | 43.3 (30.4–54.1) | 43.0 (28.9–53.0) | 0.427 |
| Baseline platelets (x109/L) | |||
| N Eval | 512 | 512 | |
| Median (Range) | 234 (125–421) | 235 (134–497) | 0.968 |
| Baseline mononuclear cell count (x109/L) | |||
| N Eval | 512 | 510 | |
| Median (Range) | 2.3 (0.9–4.8) | 2.1 (1.0–4.7) | <0.001 |
| Use of central line, Day 5 or Day 6 | 0.670 | ||
| No | 471 (92) | 469 (91) | |
| Yes | 42 (8) | 44 (9) | |
| Two-day collection | 0.128 | ||
| No | 464 (90) | 473 (92) | |
| Yes | 49 (10) | 40 (8) | |
| Total average daily filgrastim dose per donor weight (mcg/kg) | |||
| N Eval | 511 | 503 | |
| Median (Range) | 10.5 (8.3–22.0) | 10.6 (7.3–13.7) | 0.106 |
| Volume of whole blood processed, total | 0.695 | ||
| Small, <12 L | 27 (5) | 28 (5) | |
| Standard, 12–18 L | 121 (24) | 127 (25) | |
| Large, 18> L | 364 (71) | 358 (70) | |
| Unknown | 1 (N/A) | 0 (N/A) | |
| Median (Range) | 22 (6–30) | 20 (7–32) | 0.394 |
| Months between 1st and 2nd donation | |||
| N Eval | 0 | 513 | |
| Median (Range) | 11.7 (0.3–128.1) | ||
| Recipient of 1st donation is the same as 2nd donation | |||
| No | 0 | 172 (34) | |
| Yes | 341 (66) | ||
| Same donation center | |||
| No | 0 | 11 (26) | |
| Yes | 32 (74) |
No significant differences were identified for collection characteristics at first and second donations, specifically with respect to central line use, two-day collections, average daily G-CSF use or total blood volume processed. The median inter-donation interval for PBSC collections was 11.7 months (range 0.3–128.1).
Comparison of first and second mobilizations and PBSC collections
In univariate analyses, the day 5 circulating (pre-apheresis) CD34+ cell (x106/L) count showed a trend towards lower counts for donors at second PBSC donation compared to the first (68.6 vs. 73.9; p=0.03) and a trend to lower total final CD34+ cell collection yields (x106) (556 vs. 608; p=0.02). CD34+cells/L blood processed were also marginally lower at second donation compared to the first (30.1 vs. 32.2; p=0.07), and (Table 2).
Table 2.
Cell collection outcomes for PBSC donations
| 1st donation | 2nd donation | ||
|---|---|---|---|
| Variable | N (%) | N (%) | p-value |
| Number of donors | 513 | 513 | |
| Pre-apheresis (Day 5) CD34+ cells (x106/L) | |||
| N Eval | 497 | 502 | |
| Median (Range) | 73.9 (0.3–943) | 68.6 (6.4–800) | <0.001 |
| Day 5 CD34+ cell count (x106) | |||
| N Eval | 513 | 513 | |
| Median (Range) | 586 (41.8–2480) | 549 (17.5–2823) | <0.001 |
| Day 5 CD34+/L blood processed (x106/L) | |||
| N Eval | 513 | 513 | |
| Median (Range) | 32.3 (1.7–160) | 30.1 (0.7–167) | <0.001 |
| Total CD34+ cell count (x106) | |||
| N Eval | 512 | 513 | |
| Median (Range) | 608 (41.8–2480) | 556 (17.5–2823) | <0.001 |
| Total CD34+ cell count per kg (x106) (recipient body weight) | 0.095 | ||
| N Eval | 251 | 237 | |
| Median (Range) | 8.5 (1.3–60.0) | 8.2 (1.1–43.1) | |
| Total CD34+/L blood processed (x106/L) | |||
| N Eval | 512 | 513 | |
| Median (Range) | 32.2 (1.7–160) | 30.1 (0.7–167) | <0.001 |
Using the median pre-apheresis peripheral blood CD34+ cell counts from donation 1 as the cut off for “optimal” versus “sub-optimal” mobilizers, we found that individuals who were likely to be optimal or sub-optimal mobilizers at first donation were also likely to be optimal or sub-optimal mobilizers at second donation, respectively (Table 3). Donors below 12-month inter-donation time and donors above 12-month inter-donation time were similarly distributed in the matched and mismatched pre-apheresis CD34+ counts. Further, 46% of individuals who demonstrated pre-apheresis peripheral blood CD34+ cell counts of less than 20 ×106/L at first donation also demonstrated pre-apheresis peripheral blood CD34+ cell counts of less than 20 ×106/L at second donation.
Table 3:
Pre-apheresis (Day 5) peripheral blood CD34+ cell counts (x106/L) from donation 1 vs. donation 2, comparing “sub-optimal” mobilizers (CD34+ count < 73.9) vs. “optimal” mobilizers (CD34+ count ≥ 73.9)
| Donation 2 | |||
|---|---|---|---|
| Donation 1 | CD34+ count < 73.9 | CD34+ count ≥ 73.9 | Total |
| CD34+ count < 73.9 | 205 (42%) | 41 (8%) | 246 (50%) |
| CD34+ count ≥ 73.9 | 55 (11%) | 189 (39%) | 244 (50%) |
| Total | 260 (53%) | 230 (47%) | 490 (100%) |
“Matched” donors were those with both first and second mobilization CD34+ cells counts below or with both first and second mobilization CD34+ cells above the median, 73.9/uL. “Mismatched” donors were those with discrepant first and second mobilization pre-apheresis CD34+ cells counts – i.e, one below and the other above the median, 73.9/uL.
In a sub-group of donors who donated PBSCs to the same recipient for the second time within 60 days (30/5133; 5.9%), the mean pre-apheresis peripheral blood CD34+ cell counts were 146.6 ×106/L (±206.8) and 91.4 ×106/L (±134.7) at first and second mobilizations, with a mean decrease in mobilized CD34+ cells of 57.5 ×106/L (±125). Among PBSC donors who subsequently donated to the same recipient beyond the 60 days (483/513), the mean pre-apheresis peripheral blood CD34+ cell counts were 97.8 ×106/L (±77) and 91.8 ×106/L (±84) at first and second mobilizations, with a mean decrease in mobilized CD34+ cells of 5.6 ×106/L (±75.7).
In a multivariate analyses, donors with an inter-donation interval of ≥12 months, demonstrated higher CD34+cells/L blood processed compared to those donating within a year (mean ratio (MR) 1.14, p<0.0001). Change in donor BMI was also a predictor for PBSC yields. If donor BMI increased at second donation, so did the CD34+cells/L blood processed (MR: 1.15, p =0.01). An average G-CSF dose above 960 mcg was also associated with an increase in CD34+cells/L blood processed compared to donors who received less than 960 mcg (MR: 1.12, p=0.009). (Table 4a).
Table 4a:
Model for total CD34+ cells (x106/L) processed for 2nd donation (Days 5+6 apheresis bag cell counts)
| Variable | Level | n | Mean Ratio | Lower CL | Upper CL | p-value |
|---|---|---|---|---|---|---|
| Change in BMI classification from 1st to 2nd donation | No change | 405 | 1.00: Reference | |||
| Change in BMI classification from 1st to 2nd donation | Decrease in BMI group | 28 | 0.74 | 0.63 | 0.86 | <0.0001 |
| Change in BMI classification from 1st to 2nd donation | Increase in BMI group | 67 | 1.15 | 1.03 | 1.28 | 0.010 |
| Time between 1st and 2nd donation (months) | <12 | 252 | 1.00: Reference | |||
| Time between 1st and 2nd donation (months) | >=12 | 248 | 1.15 | 1.07 | 1.24 | <0.0001 |
| Total average daily filgrastim dose (mcg) for 2nd donation | <=960 | 381 | 1.00: Reference | |||
| Total average daily filgrastim dose (mcg) for 2nd donation | >960 | 119 | 1.13 | 1.04 | 1.22 | 0.005 |
Both models are adjusted for the first donation CD34+ cells/L (day 5+day 6 for 4a, day 5 for 4b)
Pre-apheresis peripheral blood CD34+ cell counts on Day 5 of the second donation were also affected by the inter-donation interval, with higher cell counts associated with a longer time interval (≥12 months) between donations (MR: 1.23, p<0.0001). Further, independent of the inter-donation interval, G-CSF doses greater than 960mcg per day for the second donation was associated with higher pre-apheresis CD34+ cells at second donation (MR: 1.26, p<0.0001); as was a higher baseline WBC count at the second donation (>6.9K/μL; 1.3, p<0.0001) (Table 4b).
Table 4b:
Model for Pre-apheresis CD34+ cells (x106/L) for 2nd donation (Day 5 peripheral blood cell counts)
| Variable | Level | n | Mean Ratio | Lower CL | Upper CL | p-value |
|---|---|---|---|---|---|---|
| Time between 1st and 2nd donation (months) | <12 | 240 | 1.00: Reference | |||
| Time between 1st and 2nd donation (months) | >=12 | 238 | 1.23 | 1.10 | 1.36 | <0.0001 |
| Total average daily filgrastim dose (mcg) for 2nd donation | <=960 | 364 | 1.00: Reference | |||
| Total average daily filgrastim dose (mcg) for 2nd donation | >960 | 114 | 1.26 | 1.11 | 1.43 | <0.0001 |
| Baseline WBC (x109/L) for 2nd donation | <=5.0 | 129 | 1.00: Reference | |||
| Baseline WBC (x109/L) for 2nd donation | >5.0 to <=5.9 | 117 | 1.02 | 0.88 | 1.18 | 0.764 |
| Baseline WBC (x109/L) for 2nd donation | >5.9 to <=6.9 | 113 | 1.18 | 1.02 | 1.37 | 0.025 |
| Baseline WBC (x109/L) for 2nd donation | >6.9 | 119 | 1.30 | 1.12 | 1.51 | <0.0001 |
Both models are adjusted for the first donation CD34+ cells/L (day 5+day 6 for 4a, day 5 for 4b)
Bone marrow donor characteristics and collection outcomes
For 43 second BM donations from 2006 to 2017, donor demographics were similar to those of PBSC donors, with a majority being Caucasian males under 40 years of age (Table 5). Baseline CBC and other counts were also similar at first and second donations. The median TNC (X109) requested for second BM collections was no different from first-time collections 12.6 (range: 4.2–35.0) vs. 12.1 (range: 2.4–35.0), respectively (p=0.84). However, the TNC/mL (X106) was lower for the second donation compared to the first donation (16.8, Range: 8.1–35.1 vs. 22.3, Range: 8.9–34.6; p=0.02). The median total product volume and collection duration were marginally higher for second harvests, however the differences were not statistically significant. The median TNC (X109) collected at first and second donations were 16.4 (3.0–50.3) vs. 16.8 (4.8–47.1), respectively (p=0.9) (Table 5). The median inter-donation interval for BM collections was 12.2 months (range 1.4–104.4).
Table 5:
Demographics and cell collection outcomes for two-time domestic BM donors with a first donation between 2006 and 2017
| 1st donation | 2nd donation | ||
|---|---|---|---|
| Variable | N (%) | N (%) | p-value |
| Number of donors | 43 | 43 | |
| Number of centers | 28 | 26 | |
| Sex | |||
| Female | 12 (28) | 12 (28) | |
| Male | 31 (72) | 31 (72) | |
| Donor age at donation | 0.0.172 | ||
| 18 to 29 | 17 (40) | 15 (35) | |
| 30 to 39 | 16 (37) | 15 (35) | |
| 40 to 49 | 10 (23) | 13 (30) | |
| Median (Range) | 33 (19–47) | 33 (21–49) | <0.001 |
| Race | |||
| Caucasian | 27 (63) | 27 (63) | |
| Hispanic | 7 (16) | 7 (16) | |
| Black/African American | 2 (5) | 2 (5) | |
| Asian/Pacific Islander | 3 (7) | 3 (7) | |
| American Indian/Alaska Native | 1 (2) | 1 (2) | |
| Other/Multiple Race | 3 (7) | 3 (7) | |
| Weight at baseline (kg) | |||
| N Eval | 43 | 43 | |
| Median (Range) | 83 (52–120) | 86 (52–120) | <0.001 |
| Body Mass Index (BMI), kg/m2 | 0.424 | ||
| Normal (18.5–24.9) | 15 (35) | 14 (33) | |
| Overweight (25–29.9) | 16 (37) | 14 (33) | |
| Obese (30+) | 12 (28) | 15 (35) | |
| Requested TNC cell count (x109) | |||
| N Eval | 21 | 18 | |
| Median (Range) | 12.1 (2.4–35.0) | 12.6 (4.2–35.0) | 1.00 |
| Baseline WBC (x109/L) | |||
| N Eval | 43 | 43 | |
| Median (Range) | 6.7 (3.3–10.1) | 5.9 (3.4–11.3) | 0.063 |
| Baseline hematocrit (%) | |||
| N Eval | 43 | 43 | |
| Median (Range) | 43.0 (37.5–48.8) | 43.1 (34.2–50.1) | 0.3129 |
| Baseline platelets (x109/L) | |||
| N Eval | 43 | 43 | |
| Median (Range) | 231 (153–339) | 242 (147–348) | 0.388 |
| Baseline mononuclear cell count (x109/L) | |||
| N Eval | 43 | 42 | |
| Median (Range) | 2.4 (1.2–4.0) | 2.4 (1.3–4.1) | 0.828 |
| Product volume without additive, mL | |||
| N Eval | 43 | 42 | |
| Median (Range) | 720.0 (232.0–1921.0) | 813.0 (276.0–1716.1) | 0.068 |
| Collection Duration, minutes | |||
| N Eval | 37 | 26 | |
| Median (Range) | 34.0 (18.0–133.0) | 46.0 (20.0–154.0) | 0.050 |
| Months between 1st and 2nd donation | |||
| N Eval | 0 | 43 | |
| Median (Range) | 12.2 (1.4–104.4) | ||
| Recipient of 1st donation is the same as 2nd donation | |||
| No | 0 | 14 (33) | |
| Yes | 29 (66) | ||
| Same donation center | |||
| No | 0 | 11 (26) | |
| Yes | 32 (74) | ||
| TNC cell count (x109) | |||
| N Eval | 42 | 42 | |
| Median (Range) | 16.4 (3.0–50.3) | 16.6 (4.8–47.1) | 0.864 |
| TNC/mL (x106/mL) | |||
| N Eval | 42 | 42 | |
| Median (Range) | 22.3 (8.9–34.6) | 16.8 (8.1–35.1) | 0.017 |
DISCUSSION
In this large study of second time unrelated donors, CD34+ cell mobilization and collection yields were found to be lower at subsequent PBSC donations. Second donation mobilization was dependent on interval between donation, first donation mobilization and collections yields, average G-CSF dose, donor BMI, and pre-apheresis WBC count. TNC concentration in second BM donations was also marginally lower than that of the first. These results are commensurate with data from previous smaller studies of second time PBSC and BM donors (Table 6) [8, 9].
Table 6:
Systematic review of second donation CD34+ cell counts/yields in healthy allogeneic BM or PBSC donors
| Study (Second donations) | Year | Filgrastim dose (mcg/kg/d) | Sample size (n) | Inter-donation interval in months, median (range) | CD34+ mobilization/collection yield | Multi-variate analysis | Other contributing factors | Reference |
|---|---|---|---|---|---|---|---|---|
| Velier, et al. | 2019 | 10 | 27 | 5.5 (1–55) | 35.6/μL (12.8–182.5/μL); versus 33.8 /μL (11.7–117.5μL) p=0.0013* | No | N/A | Transfusion |
| Stroncek, et al. | 2017 | 10 | 307 (subset analysis) | 6.1 (0.3–52.1) | 30.2 (1.7–114.2) 27.8 (0.7–122.1) p=0.007ǂ | No | Not assessed | Biol. Blood and Marrow Transplant |
| Gao, et al. | 2016 | 5 | 100 | 10 (1.1–56.23) | 2.95 (0.89–14.55) 1.3 (0.16–6.23) p=significant† | Yes | Interval, steady-state ALC, female sex | Transfus Apher Sci |
| Lown, et al. | 2013 | 10 (some Non-G BM) | 120 | 5.9 (0.7–133) | N/A; higher mean CD34 doses requested for second transplants | N/A | N/A | Haematologica |
| Chang, et al. | 2009 | 5 | 38 cases 38 controls | ?? | Cases (second time donors): 51 Controls (first time donors) 70 P<0.05* | Stratified analysis | Inter-donation interval stratified into </>9 months | Zhonghua Xue Ye Xue Za Zhi |
| Akiyama, et al. | 2006 | Non-G BM | 137 | 3.9+2 (1.4–9.6) years | 2.2±0.8 1.9±0.7 p<0.001‡ | N/A | N/A | BMT |
| Platzbecker, et al. | 2005 | 7.5 | 67 | 5 (0.1–0.47) | Men: 5.96 (2.18–15.61) 5.36 (1.79–13.34) p=ns Women: 5.00 (0.77–14.76) 3.23 (0.13–10.79) p=0.008† | Yes | PB CD34 concentration pre collection, female sex | Transfusion |
| De la Rubia, et al. | 2002 | 10 | 46 | 6.2 (0.25–47.6) | 5.35 (1.52–15.77) 3.16 (0.35–19.09) P=0.05† | No | N/A | J Hematother Stem Cell Res. |
| Tichelli, et al. | 1999 | 10 | 10 | 1.4 (0.5–12.8) | 81.2 (46–154.4) 50.4 (16.6–109.7) p=0.007* | No | Not assessed | Brit J. Haem. |
| Anderlini, et al. | 1997 | 12 | 13 | 5 (1–13) | 28 27.3 p=0.9ǂ | No | N/A | Brit J. Haem |
| Stroncek, et al. | 1996 | 7.5–10 | 12 (subset analysis) | At least 12 months apart | 77.1 (35.2–201.2) 74.8 (16.1–356.9) p=0.48* | No | Not assessed | Transfusion |
| Stroncek, et al. | 1991 | Non-G BM | 16 | 8.9 (1–43) | 29.2 vs. 20.3 p=NS§ | No | Correlation with Inter-donation interval | Transfusion |
Peripheral blood CD34+ cell counts after FILGRASTIM for 5 days (106/L);
(yield/liter processed) at First Donation vs. Second Donation;
CD34+ cells collected/kg;
X107cells/mL of marrow solution collected;
X108TNC/mL
Overall, the PBSC collection yields at second donation were somewhat less than first donation yields, but this difference was more pronounced when the time between donations was shorter. An interval less than 12 months was associated with lower Day +5 peripheral blood CD34+ cell counts and final apheresis collection yields. We hypothesize that the decrease may be multifactorial in etiology and possibly due to a combination of the following phenomena. A transient fall in bone marrow stem cell reserve may occur secondary to an apheresis procedure induced “steal”. Thereafter, consistent with speculative duration for hematopoietic stem cell replication in humans, hematopoietic stem cells rejuvenate to reach steady state levels at 9–12 months after the first donation [21, 22]. It is also possible that lower remobilization yields are due to decreased responsiveness to G-CSF at repeat exposure. This finding was described by Fiala and colleagues who demonstrated reduced remobilization in adults who received G-CSF within a span (median) of 4.6 months (range: 1–75 months). In contrast, initial mobilization with a CXCR4 antagonist was not associated with reduced remobilization [23]. It would be of interest to determine if cyclophosphamide or GRO-beta which have been shown to work through different mechanisms [24, 25] also demonstrate decreased remobilization yields within a certain inter donation period.
Second PBSC collection yields were also more likely to be low if the first donation collection yields were low. There is a lack of consensus on the definition of a “poor PBSC mobilizer” for allogeneic transplants. Most studies in autologous transplants utilize a cut-off of 20 ×106 CD34+cells/L in peripheral blood or <2×106 CD34+ cells/kg recipient body weight [26, 27]. Being under-powered to identify consequences of “poor” second mobilizations, our study used median donor peripheral blood CD34+ cell counts to delineate “optimal” vs. “suboptimal” mobilizers. While final target dose was met with the reported donations, we found that sub-optimal mobilizers at first donation (with pre-apheresis CD34+ cell counts <73.9 ×106/L) appear to donate suboptimal numbers of hematopoietic stem cells at their subsequent donation. This may be of significant clinical relevance as centers may wish to identify alternate donors for repeat collections if donor history indicates sub-optimal mobilization. In the absence of alternate donors, higher cytokine doses or AMD3100/Plerixafor may be added to remobilize the same donor.
In instances where donors were remobilized for the same recipients within 60 days of their first donation (potentially due to primary graft failure), the pre-apheresis CD34+ cells counts decreased by 40% at the second collection. While final CD34+ cell yields met target doses in the second collections, this decrease may be an important consideration for clinicians who wish to remobilize donors within a very short time interval.
Increased BMI, higher total average G-CSF dose and higher baseline WBC counts were associated with higher pre-apheresis peripheral blood CD34+ cell counts and total PBSC yields at second donation. As previously described in murine studies, individuals with higher BMI likely have more mobilizable stem cells in their adipose tissue [28]. They may also receive up to 80% more G-CSF, which is dosed by actual body weight instead of ideal body weight [5, 29]. This is also evidenced by the fact that obese donors experience greater toxicities to G-CSF [30]. The explanation for an independent positive association between higher second donation baseline neutrophil counts and mobilized CD34+ cell counts is unclear. We hypothesize that this may be related to better marrow reserve in individuals with baseline WBC >6.9×109/L.
Our study also found that second BM donations demonstrated lower TNC concentrations than the first. However, the final TNC collected per harvest was equivalent. Other studies have demonstrated a similar decrease in BM TNC/mL at repeat harvest, especially when performed within 3 months of the first harvest. Higher collection volumes and harvest duration were needed to meet target TNC at second donations [12, 19]. A recent CIBMTR study found a significant decline in the quality of BM products, as defined by the concentration of total nucleated cells (TNCs) between 1994 and 2016, likely due to fewer BM harvest procedures over the years. The study also found that higher volume centers (performing >30 collections per era) had better-quality harvests with higher concentrations of TNCs collected [31]. In another retrospective single center analysis of donor factors affecting TNC at harvest, a higher hemoglobin, higher mononuclear cell fraction, more blood donations, smoking status (yes) and a higher body surface area, lower age and a negative CMV status were predictive of a higher TNC, after adjusting for collection volume[32]. Even though our data had a larger number of repeat bone marrow collections than was reported in prior studies, our small sample size relative to repeat PBSC collections precluded further analyses, specifically pertaining to center effects and such.
There were additional study limitations. In about a third of the cases, recipients of the second donation were different from those at first donation, likely changing TNC requirements between donations. Further, engraftment data in recipients were not accessed as part of the current dataset and hence variable outcomes were unevaluable at first compared to second donation. Despite decreases in BM TNC concentrations, it is likely that our second time BM donors underwent larger total volume collections with longer BM harvests (as noted from the higher median values for these parameters at second compared to first donation). These data failed to reach statistical significance due to limited numbers. The need for more frequent day 2 apheresis procedures in repeat PBSC donors could also not be verified in our study. Several centers routinely performed day 2 collections in their donors as a precautionary measure, despite reaching target dose on Day 1.
In summary, in this large retrospective study of second time unrelated PBSC and BM donors, total mobilized PBSC and TNC/mL were lower at second donation. A shorter inter-donation interval and a decrease in BMI were confirmed to be associated with lower second PBSC mobilization and collection. Further, sub-optimal mobilizers at first donation appear to donate suboptimal numbers of stem and progenitor cells at their subsequent donation. Some of these parameters may be improved by increasing G-CSF dose within permissible limits. However in several instances, especially if a remobilization is necessary to collect a second graft for a recipient within the first 60 days of the original PBSC transplant, graft enhancement strategies may not be feasible and selection of a different donor could be considered.
HIGHLIGHTS.
Mobilized PBSC yields and bone marrow total cell concentrations are lower in second time donors.
Longer inter-donation interval, higher BMI and higher G-CSF dose increase second donation yields.
ACKNOWLEDGEMENTS
The CIBMTR is supported primarily by Public Health Service U24CA076518 from the National Cancer Institute (NCI), the National Heart, Lung and Blood Institute (NHLBI) and the National Institute of Allergy and Infectious Diseases (NIAID); U24HL138660 from NHLBI and NCI; OT3HL147741, and U01HL128568 from the NHLBI; HHSH250201700006C, and HHSH250201700007C from the Health Resources and Services Administration (HRSA); and N00014-18-1-2850, N00014-18-1-2888, and N00014-20-1-2705 from the Office of Naval Research. Additional federal support is provided by P01CA111412, R01CA152108, R01CA215134, R01CA218285, R01CA231141, R01AI128775, R01HL126589, R01HL129472, R01HL130388, R01HL131731, U01AI069197, U01AI126612, and BARDA. Support is also provided by Be the Match Foundation, Boston Children’s Hospital, Dana Farber, St. Baldrick’s Foundation, Stanford University, the Medical College of Wisconsin the National Marrow Donor Program, and from the following commercial entities: AbbVie; Actinium Pharmaceuticals, Inc.; Adaptive Biotechnologies; Adienne SA; Allovir, Inc.; Amgen Inc.; Angiocrine Bioscience; Astellas Pharma US; AstraZeneca; Atara Biotherapeutics, Inc.; bluebird bio, Inc.; Bristol Myers Squibb Co.; Celgene Corp.; CSL Behring; CytoSen Therapeutics, Inc.; Daiichi Sankyo Co., Ltd.; Gamida-Cell, Ltd.; Genentech Inc; HistoGenetics, Inc.; Incyte Corporation; Janssen Biotech, Inc.; Jazz Pharmaceuticals, Inc.; Johnson & Johnson; Kiadis Pharma; Kite, a Gilead Company; Kyowa Kirin; Legend Biotech; Magenta Therapeutics; Mallinckrodt LLC; Merck & Company, Inc.; Merck Sharp & Dohme Corp.; Millennium, the Takeda Oncology Co.; Miltenyi Biotec, Inc.; Novartis Pharmaceuticals Corporation; Omeros Corporation; Oncoimmune, Inc.; Orca Biosystems, Inc.; Pfizer, Inc.; Pharmacyclics, LLC; Sanofi Genzyme; Shire; Sobi, Inc.; Stemcyte; Takeda Pharma; Terumo BCT; Viracor Eurofins; Vor Bio Pharma; Xenikos BV; The views expressed in this article do not reflect the official policy or position of the National Institute of Health, the Department of the Navy, the Department of Defense, Health Resources and Services Administration (HRSA) or any other agency of the U.S. Government.
Footnotes
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CONFLICTS OF INTEREST
Dr. Shaw reports grants from NMDP, during the conduct of the study; personal fees from Orca Biosystems, personal fees from Merck, Sharpe and Dohme, other from Other, outside the submitted work.
Dr. Pulsipher reports personal fees from Novartis, personal fees from Bellicum, grants and personal fees from Miltenyi, grants from Adaptive, personal fees from Jasper Therapeutics, personal fees from Mesoblast, outside the submitted work.
All other authors have no conflicts to disclose.
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