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IDH1/2 mutations in remission predict AML relapse
Table 2. Risk of relapse according to the presence of persistent mutations in different genes (Fine and Gray regression model).
HR
Age ≥ 60 years 0.99 Female gender 1.23
CRIDH+ 3.89 CRFLT3+ 12.6
CRNPM1+ 1.38 CRDNMT3A+ 2.01
Univariate 95% CI
0.96 to 1.03
0.56 to 2.67 1.98 to 7.62 1.66 to 95.1 0.25 to 7.75 0.92 to 4.39
P value HR 0.9
0.61
<0.01 4.45
0.01 20.2 0.71
0.08
Multivariate 95% CI
2.15 to 9.19 3.99 to 102
P value
<0.01 <0.01
HR; hazard ratio, CI; confidence interval, CRIDH+; persistent IDH1/2 mutation in CR or CRi, CRFLT3+; persistent FLT3-ITD mutation in CR or CRi, CRNPM1+; persistent NPM1 mutation in CR or CRi, CRDNMT3A+; persistent DNMT3A mutation in CR or CRi.
CRFLT3+ also demonstrated an increased risk of relapse. By multivariate analysis, CRIDH+ and CRFLT3+ remained signifi- cant for an increased risk of relapse.
We also assessed the dynamic changes of clonal archi- tecture in 25 CRIDH+ patients who relapsed. Comparing mutational profiles at CR/CRi and relapse, four patients acquired novel mutations at relapse. These mutations were ERBB2 p.R784C (MAF: 12.3%), FLT3 p.D835Y (1.5%), TP53 p.G245D (3.8%) and WT1 p.K467fs (12.2%). These mutations showed subclonal fraction patterns com- pared with the MAF of IDH1/2 mutation at relapse.
Flow cytometry is comparable to next-generation sequencing in predicting relapse
We compared molecular test results to those of multi- parametric flow cytometry (FC) immunophenotyping in CR/CRi bone marrow specimens. Flow cytometric results were available for a total of 79 patients. Minimal residual disease (MRD) determination by FC has been described previously.32,33 The sensitivity of the flow cytometry was validated to 0.1% - 0.01% depending on the leukemic cell phenotype. According to FC, 19 (26%) patients had MRD, 55 (76%) were MRD-negative and results were indetermi- nate in five patients. Among 74 patients in whom both FC and molecular MRD tests were performed, the results were concordant in 61 (82%) patients and discordant in 13 (18%) patients with a statistically significant association (P<0.01). Of the 13 patients with discordant FC and molecular testing MRD results, ten patients were positive by FC only and three patients were positive by molecular testing only. Four of the five patients for whom FC was indeterminate with regards to MRD had a persistent IDH2 p.R140Q mutation with various MAF values (median 12.5%; range, 1 to 28.5%) and all of them relapsed. Similarly to CRIDH+ patients, those who were positive for MRD assessed by flow cytometry (FC+) showed an increased risk of relapse compared to patients who were negative for MRD by flow cytometry (FC–) after 1 year of follow-up (63% versus 27%; hazard ratio, 4.24; 95% con- fidence interval: 2.22 to 8.13; P<0.01). Patients with posi- tive results in both methods (CRIDH+/FC+) had a significant- ly higher risk of relapse compared to those with discor- dant results (CRIDH+/FC– or CRIDH-/FC+) or negative results in both methods (CRIDH-/FC–) (Figure 2 and Table 3).
Discussion
IDH1 and IDH2 mutations are not uncommon in AML. In addition, IDH1/2 mutations can be found in the pre-
Table 3. Risk of relapse with respect to presence or absence of a per- sistent IDH1/2 mutation and flow cytometry determined minimal residual disease status (Fine and Gray regression model).
Group HR
CRIDH+/FC+ (n=16) Reference
CRIDH+/FC- or
CRIDH-/FC+ (n=13) 0.36
CRIDH-/FC- (n=45) 0.17
95% CI
0.15 to 0.87
0.08 to 0.34
P value
0.02
<0.01
CRIDH+; persistent IDH1 or IDH2 mutation in remission, CRIDH-; no detectable IDH1 or IDH2 mutation in remission, FC+; positive for minimal residual disease by flow cytom-
-
etry, FC ; negative for minimal residual disease by flow cytometry.
leukemic clone in individuals without pathology-proven AML or even in healthy individuals as a sign of age-related clonal hematopoiesis.13,34-36 For these reasons, in this study, we only selected AML patients with an IDH1/2 mutation as a predominant clone (MAF >10%) in pretreatment sam- ples to minimize the effect on our analysis of subclonal IDH1/2 mutations.
In patients with AML associated with IDH1/2 muta- tions, karyotyping is not a preferred method for monitor- ing persistent aberrancy during remission for at least two reasons: cytogenetic analysis is less sensitive and IDH1/2 mutations are enriched in AML with a normal kary- otype.5,8,11,37 In support of this statement, 68% of patients had a diploid karyotype at diagnosis. Out of 24 patients who had cytogenetic abnormalities in pretreatment sam- ples, only two had persistent cytogenetic abnormalities in the remission sample. Therefore, follow-up with more sensitive methods is necessary to monitor for MRD.
In this cohort of patients, IDH2 mutations (69%) were more common than IDH1 mutations (31%). In the IDH2 group, mutations at codon 140 were far more frequent than R172 mutations in an approximately 5.8 to 1 ratio. IDH1 mutations were present in almost one-third of patients. These frequency data are consistent with those from other studies of AML in the literature.5,11,37 The medi- an MAF of an IDH1/2 mutation was 43.8%, indicating that the IDH1/2 mutation was the predominant clone in most patients. The median MAF of the IDH1 R132 muta- tion (39.2%) was slightly lower than that of IDH2 muta- tions (44.1% and 42.5% for IDH2 R140 and R172 muta- tions, respectively).
Persistent IDH1/2 mutations in patients with AML who are in complete remission (CRIDH+) have been reported by others.18,19 We observed that approximately 40% of AML patients in remission had persistent IDH1/2 mutations with decreased MAF regardless of IDH mutation subtype (IDH1 R132, IDH2 R140 and IDH2 R172) or treatment
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