Patients and transplant procedures
A total of 754 patients with AML are included in this analysis, of whom 617 received FluTreo and 137 FluTBI conditioning. Patients in the FluTBI group were significantly younger with a median age of 53.7 (range, 40.1–70.7) vs. 60.7 (range 40.1–77.5) years. They had been transplanted a median of two years earlier (2014 vs. 2016) and had longer follow-up (median 45.9 vs. 26.9 months), Table 1. Additional statistically significant differences between the groups included a higher proportion of MSD with FluTBI (64.2% vs. 36.3%, p < 0.0001) as opposed to 10/10 MUD (35.8% vs. 63.7%, p < 0.0001), a shorter time from diagnosis to HSCT (3.8 (range, 1.8–16.2) vs. 4.7 (range, 1.7–22.9 months)) and a higher proportion of patients with de novo AML (84.7% vs. 76%). The groups did not differ significantly in terms of adverse risk cytogenetics according to European LeukemiaNet (ELN) 2017, patient or donor sex, KPS, or pre-transplant MRD status, although information on the latter parameter was available for only 287 patients.
Table 1
Patient, donor, and transplant characteristics according to conditioning regimen for all patients
|
FluTBI (n = 137)
|
FluTreo (n = 617)
|
P
|
Median patient age, years (range)
|
53.7 (40.1–70.7)
|
60.7 (40.1–77.5)
|
< 0.0001
|
Karnofsky performance score
|
|
|
|
<90%
|
27 (20.1%)
|
133 (22.2%)
|
0.60
|
≥90%
|
107 (79.9%)
|
465 (77.8%)
|
|
Missing
|
3
|
19
|
|
Diagnosis
|
|
|
|
De novo AML
|
116 (84.7%)
|
469 (76%)
|
0.028
|
Secondary AML
|
21 (15.3%)
|
148 (24%)
|
|
Cytogenetic risk group
|
|
|
|
Good
|
4 (3.7%)
|
15 (3.4%)
|
0.074
|
Intermediate
|
75 (70.1%)
|
256 (58.9%)
|
|
Poor
|
28 (26.2%)
|
164 (37.7%)
|
|
NA/failed
|
30
|
182
|
|
Not adverse
|
109 (79.6%)
|
453 (73.4%)
|
0.14
|
Adverse
|
28 (20.4%)
|
164 (26.6%)
|
|
Median interval from diagnosis to HSCT, months (range)
|
3.8 (1.8–16.2)
|
4.7 (1.7–22.9)
|
< 0.0001
|
Median year of HSCT (range)
|
2014 (2009–2019)
|
2016 (2009–2019)
|
< 0.0001
|
MRD status pre-transplant
|
|
|
|
MRD negative
|
31 (64.6%)
|
143 (59.8%)
|
0.54
|
MRD positive
|
17 (35.4%)
|
96 (40.2%)
|
|
Missing
|
89
|
378
|
|
Donor
|
|
|
|
Matched sibling
|
88 (64.2%)
|
224 (36.3%)
|
< 0.0001
|
10/10 HLA matched unrelated
|
49 (35.8%)
|
393 (63.7%)
|
|
Patient sex
|
|
|
|
Male
|
84 (61.3%)
|
329 (53.3%)
|
0.089
|
Female
|
53 (38.7%)
|
288 (46.7%)
|
|
Donor/patient sex
|
|
|
|
Female/male
|
26 (19%)
|
107 (17.4%)
|
0.66
|
Other combinations
|
111 (81%)
|
508 (82.6%)
|
|
Missing
|
0
|
2
|
|
Donor/patient CMV status
|
|
|
|
Donor negative/patient negative
|
34 (26.0%)
|
109 (17.9%)
|
0.11
|
Donor positive/patient negative
|
11 (8.4%)
|
37 (6.1%)
|
|
Donor negative/patient positive
|
30 (22.9%)
|
155 (25.6%)
|
|
Donor positive/patient positive
|
56 (42.7%)
|
307 (50.5%)
|
|
Missing
|
6
|
9
|
|
TBI fractions
|
|
NA
|
|
4 x 2 Gy
|
40 (29.2%)
|
|
|
2 x 4 Gy
|
16 (11.7%)
|
|
|
unknown
|
81 (59.1%)
|
|
|
Treosulfan dose
|
NA
|
|
|
3 x 10 g/m2
|
|
167 (27.1%)
|
|
3 x 12 g/m2
|
|
122 (19.8%)
|
|
3 x 14 g/m2
|
|
328 (53.2%)
|
|
In vivo T-cell depletion
|
|
|
|
No
|
74 (54%)
|
202 (32.7%)
|
< 0.0001
|
ATG
|
63 (46%)
|
415 (67.3%)
|
|
GvHD prevention
|
|
|
|
Cyclosporin A + MTX
|
117 (85.4%)
|
425 (68.9%)
|
0.0003
|
Cyclosporin A + MMF
|
10 (7.3%)
|
124 (20.1%)
|
|
Other
|
10 (7.3%)
|
68 (11.0%)
|
|
Median follow-up, months [95% CI]
|
45.88 [35.83–56.96]
|
26.92 [24.19–31.03]
|
0.033
|
HLA: Human leukocyte antigen, CMV: Cytomegalovirus, TBI: Total body irradiation; ATG: Anti-thymocyte globulin, MTX: Methotrexate, MMF: Mycophenolate mofetil, CI: Confidence interval, NA: not applicable |
The major difference in relation to transplant procedures was the significantly more frequent use of in vivo TCD with ATG in the FluTreo group (67.3% vs. 46%, p < 0.0001), Table 1.
Multivariate analysis on the entire patient population
After adjusting for confounding factors in a multivariate Cox analysis (Table 2), FluTBI conditioning was associated with a significantly lower probability of relapse than FluTreo (hazard ratio (HR) 0.59 [95% CI, 0.38–0.93], p = 0.023). There was no significant difference in LFS, OS, GRFS, or acute and chronic GVHD. Adverse risk cytogenetics and year of HSCT had a significant negative impact on relapse incidence, LFS and OS. Adverse risk cytogenetics also had a significant negative impact on GRFS.
Table 2
Multivariate analysis of factors associated with outcomes on the entire patient population
Endpoint
|
Factor
|
Hazard ratio (95% CI)
|
P value
|
Relapse
|
FluTBI vs. FluTreo
|
0.59 (0.38–0.93)
|
0.023
|
|
Year of HSCT
|
0.95 (0.9-1)
|
0.034
|
|
Adverse cytogenetics
|
2.55 (1.86–3.48)
|
< 0.0001
|
NRM
|
Age (HR per 10 years)
|
1.8 (1.35–2.42)
|
< 0.0001
|
|
KPS ≥90%
|
0.43 (0.28–0.66)
|
0.0004
|
LFS
|
Age (HR per 10 years)
|
1.2 (1.02–1.41)
|
0.026
|
|
Year of HSCT
|
0.95 (0.91–0.99
|
0.009
|
|
Adverse cytogenetics
|
2 (1.53–2.61)
|
< 0.0001
|
|
KPS ≥90%
|
0.66 (0.5–0.87)
|
0.003
|
OS
|
Age (HR per 10 years)
|
1.38 (1.16–1.65)
|
0.0004
|
|
Year of HSCT
|
0.95 (0.91-1)
|
0.037
|
|
Adverse cytogenetics
|
1.83 (1.36–2.45)
|
< 0.0001
|
|
KPS ≥90%
|
0.68 (0.51–0.92)
|
0.013
|
GRFS
|
Adverse cytogenetics
|
1.72 (1.34–2.2)
|
< 0.0001
|
|
In vivo TCD
|
0.63 (0.44–0.89)
|
0.009
|
Acute GVHD II-IV
|
none
|
|
|
Chronic GVHD
|
Female donor to male recipient
|
1.63 (1.19–2.23
|
0.002
|
|
In vivo TCD
|
0.43 (0.28–0.66)
|
< 0.0001
|
HR: Hazard ratio, CI: Confidence interval, NRM: non-relapse mortality, LFS: leukemia-free survival, OS: overall survival, GVHD: graft-versus-host disease, GRFS: Survival free of grade III-IV acute GVHD, chronic GVHD, and relapse. HSCT: hematopoietic stem cell transplantation, KPS: Karnofsky performance score, TCD: T cell depletion. |
All models were adjusted for the following factors: age (per 10 years); year of transplantation; diagnosis: secondary vs. de novo AML; cytogenetics: adverse vs. not adverse risk; interval from diagnosis to transplantation; donor/recipient sex: female to male versus other combinations; Karnofsky performance status; donor type: 10/10 HLA matched unrelated vs. matched sibling; in vivo T-cell depletion. Only factors with p value < 0.05 are shown. |
Pair-match analysis on propensity score
Because of the substantial difference in patient numbers between the two conditioning groups and significant differences in demographic and transplant-related parameters, we used propensity score matching to reduce the treatment assignment bias and create two patient groups of 115 each that were comparable for all observed covariates. Patient characteristics in the FluTBI and FluTreo group were well balanced in terms of age (median 55.2 vs. 54.9 years, KPS < 90% 22.6% and 23.5%, respectively), secondary AML (13% each), adverse cytogenetics (15.7% each), female donor to male recipient (19.1% vs. 17.4%) and time from diagnosis to HSCT (median 3.8 (range, 1.8–16.2) and 4.5 (range, 1.7–16.2) months, respectively), Table 3. An identical proportion of patients in both groups received grafts from MSD (61.7%) or 10/10 HLA-MUD (38.3%). In both groups, GVHD prophylaxis consisted predominantly of cyclosporin A (CSA) plus methotrexate (85.2% for FluTBI vs. 73.9% for FluTreo, p = ns), CSA and mycophenolate mofetil were given to 8.7% and 18.3% of patients in the FluTBI and FluTreo groups, respectively (p = ns). A similar proportion of patients in both groups (52.2% and 53.9%) received additional in vivo T-cell depletion with ATG.
Table 3
Patient, donor, and transplant characteristics according to conditioning regimen for patients included in the propensity score analysis
|
FluTBI (n = 115)
|
FluTreo (n = 115)
|
P
|
Median patient age, years (range)
|
55.2 (40.1–70.7)
|
54.9 (40.4–74.9)
|
0.96
|
Karnofsky performance score
|
|
|
|
<90
|
26 (22.6%)
|
27 (23.5%)
|
0.88
|
>=90
|
89 (77.4%)
|
88 (76.5%)
|
|
Diagnosis
|
|
|
|
De novo AML
|
100 (87%)
|
100 (87%)
|
1
|
Secondary AML
|
15 (13%)
|
15 (13%)
|
|
Cytogenetic risk group
|
|
|
|
Good
|
4 (4.5%)
|
5 (6.5%)
|
|
Intermediate
|
66 (75.0%)
|
54 (70.1%)
|
|
Poor
|
18 (20.5%)
|
18 (23.4%)
|
|
NA/failed
|
27
|
38
|
|
Not adverse
|
97 (84.3%)
|
97 (84.3%)
|
1
|
Adverse
|
18 (15.7%)
|
18 (15.7%)
|
|
FLT3 ITD
|
|
|
|
negative
|
65 (77.4%)
|
50 (67.6%)
|
0.17
|
positive
|
19 (22.6%)
|
24 (32.4%)
|
|
missing
|
31
|
41
|
|
NPM1
|
|
|
|
wildtype
|
64 (76.2%)
|
50 (67.6%)
|
0.39
|
mutated
|
20 (23.8%)
|
21 (30%)
|
|
missing
|
31
|
45
|
|
Median interval from diagnosis to HSCT, months (range)
|
3.8 (1.8–16.2)
|
4.5 (1.7–16.2)
|
0.15
|
Median year of HSCT (range)
|
2014 (2009–2019)
|
2016 (2009–2019)
|
0.005
|
MRD status pre-transplant
|
|
|
|
MRD negative
|
37 (61.7%)
|
30 (58.8%)
|
0.76
|
MRD positive
|
23 (38.3%)
|
21 (41.2%)
|
|
Missing
|
55
|
64
|
|
Donor
|
|
|
|
Matched sibling
|
71 (61.7%)
|
71 (61.7%)
|
1
|
10/10 HLA matched unrelated
|
44 (38.3%)
|
44 (38.3%)
|
|
Patient sex
|
|
|
|
Male
|
68 (59.1%)
|
64 (55.7%)
|
0.59
|
Female
|
47 (40.9%)
|
51 (44.3%)
|
|
Donor/patient sex
|
70 (60.9%)
|
71 (61.7%)
|
0.89
|
Female/male
|
22 (19.1%)
|
20 (17.4%)
|
0.73
|
Other combinations
|
93 (80.9%)
|
95 (82.6%)
|
|
Donor/patient CMV status
|
|
|
|
Donor negative/patient positive
|
27 (24.3%)
|
28 (24.6%)
|
0.97
|
Other combinations
|
84 (75.7%)
|
86 (75.4%)
|
|
Missing
|
4
|
1
|
|
TBI fractions
|
|
NA
|
|
4 x 2 Gy
|
33 (28.7%)
|
|
|
2 x 4 Gy
|
15 (13.0%)
|
|
|
unknown
|
67 (58.3%)
|
|
|
Treosulfan dose
|
NA
|
|
|
3 x 10 g/m2
|
|
27 (23.5%)
|
|
3 x 12 g/m2
|
|
23 (20.0%)
|
|
3 x 14 g/m2
|
|
65 (56.5%)
|
|
In vivo T-cell depletion
|
|
|
|
No
|
60 (52.2%)
|
62 (53.9%)
|
0.79
|
ATG
|
55 (47.8%)
|
53 (46.1%)
|
|
GVHD prevention
|
|
|
|
Cyclosporin A + MTX
|
98 (85.2%)
|
85 (73.9%)
|
0.08
|
Cyclosporin A + MMF
|
10 (8.7%)
|
21 (18.3%)
|
|
Other
|
7 (6.1%)
|
9 (7.8%)
|
|
Median follow-up, months [95% CI]
|
42.37 [31.52–53.77]
|
23.2 [20.44–32.74]
|
0.14
|
HLA: Human leukocyte antigen; CMV: Cytomegalovirus; ATG: Anti-thymocyte globulin; TBI: Total body irradiation; MTX: Methotrexate; MMF: Mycophenolate mofetil, CI: Confidence interval; NA: Not applicable |
All but one patient in each group engrafted. Median follow-up of living patients was 42.4 months (range, 31.5–53.8) in the FluTBI and 23.2 months (range, 20.4–32.7) in the FluTreo group (p = 0.14). FluTBI was associated with a significantly lower CIR of 18.3% vs. 34.7% in FluTreo (p = 0.018, HR 0.51 (95% CI, 0.29–0.89)), but a higher NRM of 16.8% vs. 5.3%, p = 0.02, HR 3.0 (95% CI, 1.19–7.59), Fig. 1A-B. This difference in NRM was due exclusively to the higher NRM in patients ≥ 55 years of age (Table 4). LFS and OS were similar in the FluTBI and FluTreo groups (64.9% vs. 60.0%, HR 0.84 (95% CI, 0.54–1.21) and 66.9% vs. 67.8%, HR 1.08 (95% CI, 0.67–1.75)), respectively, Fig. 1C-D. Infection was the leading cause of death following FluTBI (n = 12, 34.3% vs. n = 3, 9.4% with FluTreo), whereas AML recurrence was the predominant cause of death in the FluTreo group (n = 15, 46.9% vs. n = 10, 28.6%). The frequency of death due to GVHD, multiorgan failure or interstitial pneumonitis did not differ between the two groups. Two patients developed a secondary malignancy after TBI conditioning, results not shown.
Table 4
Univariate analysis by age group for the pair-match analysis
|
|
FluTreo (n = 58)
|
FluTBI (n = 56)
|
FluTBI vs FluTreo
HR (95% CI)
|
p (cluster = pair)
|
Age < 55 years
|
Relapse
|
33.6%[20.9–46.9]
|
20.5%[10.4–33]
|
0.51 (0.23–1.13)
|
0.10
|
|
NRM
|
4.7%[0.8–14.6]
|
6%[1.5–15]
|
1.68 (0.29–9.76)
|
0.57
|
|
LFS
|
61.7%[46.3–73.8]
|
73.5%[58.7–83.8]
|
0.62 (0.3–1.28)
|
0.19
|
|
OS
|
67%[50.1–79.3]
|
77.2%[62.4–86.7]
|
0.65 (0.3–1.42)
|
0.28
|
|
GRFS
|
46.6%[31.4–60.4]
|
59.7%[44.6–72]
|
0.69 (0.41–1.18)
|
0.18
|
|
Acute GVHD II-IV
|
21.4%[11.8–33]
|
20.1%[10.7–31.7]
|
0.89 (0.37–2.14)
|
0.79
|
|
Acute GVHD III-IV
|
5.4%[1.4–13.5]
|
7.3%[2.3–16.3]
|
1.28 (0.28–5.72)
|
0.75
|
|
Chronic GVHD
|
54.7%[38.3–68.4]
|
35.7%[22.1–49.5]
|
0.51 (0.29–0.93)
|
0.027
|
|
Extensive chronic GVHD
|
19.6%[8.8–33.6]
|
10.7%[3.8–21.6]
|
0.64 (0.24–1.74)
|
0.39
|
|
|
FluTreo (n = 57)
|
FluTBI (n = 59)
|
FluTBI vs FluTreo
HR (95% CI)
|
p (cluster = pair)
|
Age > 55 years
|
Relapse
|
35.7%[21.9–49.8]
|
16.3%[7.3–28.5]
|
0.52 (0.24–1.13)
|
0.10
|
|
NRM
|
5.8%[1.5–14.7]
|
27.6%[15.9–40.7]
|
3.74 (1.23–11.43)
|
0.02
|
|
LFS
|
58.4%[42.7–71.3]
|
56%[40.6–68.9]
|
1.09 (0.62–1.91)
|
0.78
|
|
OS
|
68.7%[51.6–80.9]
|
56.2%[40.5–69.3]
|
1.67 (0.89–3.15)
|
0.11
|
|
GRFS
|
45%[30.1–58.8]
|
40.4%[26.2–54.2]
|
0.98 (0.62–1.55)
|
0.92
|
|
Acute GVHD II-IV
|
20%[10.6–31.5]
|
25.4%[15.1–37.1]
|
1.21 (0.57–2.59)
|
0.62
|
|
Acute GVHD III-IV
|
12.7%[5.5–23]
|
5.1%[1.3–12.9]
|
0.34 (0.09–1.31)
|
0.12
|
|
Chronic GVHD
|
39%[24.3–53.4]
|
49.5%[34.4–63]
|
1.31 (0.78–2.21)
|
0.3
|
|
Extensive chronic GVHD
|
19.7%[8.9–33.5]
|
22.7%[12-35.5]
|
0.91 (0.45–1.82)
|
0.78
|
NRM: Non-relapse mortality; LFS: Leukemia-free survival; OS: Overall survival; GVHD: Graft-versus-host disease; GRFS: Survival free of grade III-IV acute GVHD, chronic GVHD, and relapse. All results are at 2 years except acute GVHD at 180 days post HSCT. |
There was no statistically significant difference between FluTBI and FluTreo in the CI of acute GVHD II-IV (22.8% vs. 20.7%, HR 1.05), GVHD III-IV (6.2% vs. 9.0%, HR 0.59), chronic GVHD (42.6% vs. 47.5%, HR 0.81) or extensive chronic GVHD (16.8% vs. 19.6%, HR 0.76), results not shown, resulting in similar GRFS of 50.3% and 45.6%, HR 0.83, respectively (Fig. 1E).