Single monosomy as a relatively better survival factor in acute myeloid leukemia patients with monosomal karyotype

Abstract

Monosomal karyotype (MK) defined by either [= or >, slanted]2 autosomal monosomies or single monosomy with at least one additional structural chromosomal abnormality is associated with a dismal prognosis in patients with acute myeloid leukemia (AML). It was detected in 174 of 3041 AML patients in South Korean Registry. A total of 119 patients who had received induction therapy were finally analyzed to evaluate the predictive factors for a positive prognosis. On multivariate analysis, single monosomy, the absence of abn(17p), [= or >, slanted]10% of cells with normal metaphase and the achievement of a complete remission (CR) after induction therapy were significant factors for more favorable outcomes. Especially, single monosomy remained as a significantly independent prognostic factor for superior survival in both patients who received allogeneic hematopoietic stem cell transplantation (allo-HSCT) in CR and who did not. Allo-HSCT in CR improved overall survival significantly only in patients with a single monosomy. Our results suggest that MK-AML may be biologically different according to the karyotypic subtype and that allo-HSCT in CR should be strongly recommended to patients with a single monosomy. For other patients, more prudent treatment strategies should be examined. Furthermore, the biological mechanism by which a single monosomy influences survival should be investigated.

OPEN

Citation: Blood Cancer Journal (2015) 5, e358; doi:http://dx.doi.org/10.1038/bcj.2015.84

Web End =10.1038/bcj.2015.84

http://www.nature.com/bcj

Web End =www.nature.com/bcj

JE Jang1, YH Min1, J Yoon2, I Kim3, J-H Lee4, CW Jung5, H-J Shin6, WS Lee7, JH Lee8, D-S Hong9, H-J Kim10, H-J Kim2, S Park3, K-H Lee4, JH Jang5, JS Chung6, SM Lee7, J Park8, SK Park9, J-S Ahn10, W-S Min2 and J-W Cheong1on behalf of the Korean Society of Hematology AML/MDS Working Party

Monosomal karyotype (MK) dened by either 2 autosomal monosomies or single monosomy with at least one additional structural chromosomal abnormality is associated with a dismal prognosis in patients with acute myeloid leukemia (AML). It was detected in 174 of 3041 AML patients in South Korean Registry. A total of 119 patients who had received induction therapy were nally analyzed to evaluate the predictive factors for a positive prognosis. On multivariate analysis, single monosomy, the absence of abn(17p), 10% of cells with normal metaphase and the achievement of a complete remission (CR) after induction therapy were signicant factors for more favorable outcomes. Especially, single monosomy remained as a signicantly independent prognostic factor for superior survival in both patients who received allogeneic hematopoietic stem cell transplantation (allo-HSCT) in CR and who did not. Allo-HSCT in CR improved overall survival signicantly only in patients with a single monosomy. Our results suggest that MK-AML may be biologically different according to the karyotypic subtype and that allo-HSCT in CR should be strongly recommended to patients with a single monosomy. For other patients, more prudent treatment strategies should be examined.

Blood Cancer Journal (2015) 5, e358; doi:http://dx.doi.org/10.1038/bcj.2015.84

Web End =10.1038/bcj.2015.84 ; published online 16 October 2015

INTRODUCTION

Although several different cytogenetic classications exist for acute myeloid leukemia (AML), it has been generally agreed that specic cytogenetic abnormalities result in unfavorable prog-noses. Adverse cytogenetic risk factors include 5/5q deletion (del (5q)), 7/7q deletion (del(7q)), 17/17p abnormality (abn(17p)), inv(3)(q21q26/t(3;3)(q21;q26) and complex karyotype (CK).14

Recently, monosomal karyotype (MK) has been shown to be associated with a dismal prognosis in AML, and it has gotten another prognostic value in AML patients compared with CK.59

This new category is dened by either the presence of two autosomal monosomies or one monosomy with at least one additional structural chromosomal abnormality (in the absence of core-binding factor AML and acute promyelocytic leukemia).5 Although a higher percent of cells with normal metaphases or absence of abn(17p) or 5/del(5q) in MK-AML may be associated with prognosis,10,11 studies for clinical signicance according to the karyotypic heterogeneity or subtype of MK is limited. The benets of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with MK have also been controversial. Several retrospective analyses have suggested that allo-HSCT would be associated with improved survival.12,13 In contrast,

Kayser et al.7 reported no signicant benet from allo-HSCT in patients achieving complete remission (CR) after induction therapy.

Therefore, to clarify the predictors of improved outcome and to determine appropriate indication for allo-HSCT for MK-AML patients, this study investigated the inuence of specic clinical and karyotypic characteristics on prognosis, as well as proper therapeutic strategies for MK-AML patients.

PATIENTS AND METHODS Patients

For this study, nationwide database of Korean AML Registry, which has been operated from 2007 by the Korean Society of Hematology AML/ Myelodysplastic Syndrome Working Party, was analyzed. A total of 3041 AML patients from 28 institutions were registered at the time of analysis. The cohort included 1679 male and 1356 female, with a median age of 51 years (range, 1687 years). AML was diagnosed according to the World Health Organization denition of 420% blasts in the bone marrow (BM) or peripheral blood.14 Patients without cytogenetic analysis, those in whom cytogenetic analysis failed and those with core-binding factor abnormalities or acute promyelocytic leukemia were excluded from this study. From January 2007 to December 2011, 174 patients (5.7%) who met the

1Division of Hematology, Department of Internal Medicine, Severance Hospital, Yonsei University College of Medicine, Seoul, South Korea; 2Department of Hematology, Cancer Research Institute, Seoul St Marys Hospital, College of Medicine, The Catholic University of Korea, Seoul, South Korea; 3Division of Hematology-Medical Oncology, Department of Internal Medicine, Cancer Research Institute, Seoul National University College of Medicine, Seoul, South Korea; 4Department of Hematology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea; 5Division of Hematology/Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea; 6Division of Hematology-Oncology, Department of Internal Medicine, School of Medicine, Medical Research Institute, Pusan National University Hospital, Busan, South Korea; 7Department of Hemato-Oncology, Department of Internal Medicine, Inje University Busan Paik Hospital, Busan, South Korea; 8Department of Internal Medicine, Gachon University Gil Medical Center, Gachon University School of Medicine, Incheon, South Korea; 9Department of Internal Medicine, Division of Hematology & Oncology, Soonchunhyang University Bucheon Hospital, Bucheon, South Korea and 10Department of Hematology and Oncology, Chonnam National University Hwasun Hospital, Hwasun, South Korea. Correspondence: Professor W-S Min, Division of Hematology, Department of Internal Medicine, Catholic BMT Center, Seoul St Marys Hospital, College of Medicine, The Catholic University of Korea, 222 Banpodaero, Seochogu, Seoul 137-701, South Korea or Professor J-W Cheong, Division of Hematology, Department of Internal Medicine, Severance Hospital, Yonsei University College of Medicine, Yonsei-ro 50, Seodaemun-gu, Seoul 120-751, South Korea.

E-mail: mailto:[email protected]

Web End [email protected] or mailto:[email protected]

Web End [email protected] Received 18 August 2015; accepted 20 August 2015

ORIGINAL ARTICLE

Single monosomy as a relatively better survival factor in acute myeloid leukemia patients with monosomal karyotype

Furthermore, the biological mechanism by which a single monosomy inuences survival should be investigated.

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denition of MK-AML were selected for this study, and nally 119 patients from 10 institutions who received induction therapy were retrospectively analyzed. The study protocol was approved by each institutions institutional review board.

Cytogenetic and molecular analysisCytogenetic analysis was performed using metaphasic cells from BM aspirates obtained at diagnosis using the conventional G-banding method. Karyotype designation was based on the International System for Human Cytogenetic Nomenclature.15 Only clonal abnormalities were considered positive results. Abnormalities were considered clonal if 2 metaphases had the same aberration in the case of a structural abnormality or an extra chromosome, or if 3 metaphases shared the same abnormality in the case of a monosomy. CK was dened as 3 clonal abnormalities or 4 clonal abnormalities. The MK was dened as the presence of two autosomal monosomies or one monosomy with at least one additional structural chromosomal abnormality, as previously reported by Breems et al.5

Statistical analysisThe distribution of patients characteristics between groups was compared using the 2 or Fisher's exact tests for categorical variables and the Mann Whitney U-test for continuous variables. Overall survival (OS) was dened as the time from the date of AML diagnosis to the date of death or the last follow-up. Event-free survival (EFS) was dened for all patients and was measured from the date of AML diagnosis until treatment failure, relapse from CR or death from any cause, whichever occurred rst. Relapse-free survival (RFS) in patients achieving CR after induction chemotherapy was calculated from the date of CR achievement until the date of relapse or death from any cause. When comparing the survival of patients who underwent allo-HSCT, OS and EFS were calculated from the date of allo-HSCT. Logistic regression was used to test for the factors associated with the achievement of CR in univariate and multivariate analyses. A Kaplan Meier survival analysis was performed to estimate the probabilities of survival. Differences in survival between groups were compared using the log-rank test. Factors affecting OS, EFS and RFS were analyzed using the Cox proportional hazards model in univariate and multivariate analyses. Po0.05 was dened as statistically signicant. All statistical analyses were performed using SPSS, version 20.0 (SPSS Inc., Chicago, IL, USA).

RESULTSPatient characteristicsThe baseline characteristics of 119 MK-AML patients are summarized in Table 1. The median age was 56 years (range, 1782 years); 83 patients (69.7%) were male and 36 patients (30.3%) were female. Nineteen patients (16%) were secondary AML developed following exposure to cytotoxic agents or as a subsequent event in another hematologic disorder, and most patients (89.1%) had CK (3 clonal abnormalities). The most frequent cytogenetic abnormalities were 7/7q deletion (47.1%), and 5/5q deletion(41.2%) and 17p abnormality (17.6%) were followed. MK dened by one single autosomal monosomy with at least one structural chromosomal abnormality was detected in 44 patients (37%, single monosomy group), and MK dened by 2 autosomal monosomies was detected in 75 patients (63%, 2 monosomy group). Monosomies could be detected in every chromosome in the 2 monosomy group, but chromosomes 1, 3, 4, 6, 10, 15, 19, 21 and 22 were not affected in the single monosomy group.

Patients in the 2 monosomy group were signicantly older and exhibited lower white blood cell and platelet counts compared with those in the single monosomy group (Table 1). Most patients in the 2 monosomy group exhibited CK with a higher incidence of abn(17p) and 5/del(5q) compared with those in the single monosomy group. In contrast, the incidence of inv(3)/t(3;3) tended to be higher in the single monosomy group. There were no other signicant differences in the clinical characteristics between two groups.

Therapeutic strategies and patient responsePatients received either one or two courses of myelosuppressive induction chemotherapy; 108 (90.8%) received daunorubicin or idarubicin in combination with cytarabine or the cytarabine analog, N4-behenoyl-1--D-arabinofuranosylcytosine, 6 (5%) received cytarabine combined with etoposide and 5 (4.2%) received other chemotherapy regimens. Except 6 patients who

Table 1. Patient characteristics

Total patients, n = 119 Single monosomy, n = 44 2 monosomies, n = 75 P-value

Median age (years) (range) 56 (1782) 45.5 (1778) 60 (2382) 0.001 o 60, n (%) 69 (58.0) 34 (77.3) 35 (46.7) 60, n (%) 50 (42.0) 10 (22.7) 40 (53.3)

SexMale/female 83/36 26/18 57/18 0.064

Type of AMLDe novo, n (%) 100 (84.0) 38 (86.4) 62 (82.7) 0.595 Secondary, n (%) 19 (16.0) 6 (13.3) 13 (17.3)

WBC (109/l) median (range) (n = 118) 5.83 (0.54316.2) 10.41 (0.5485.15) 3.68 (0.96316.2) 0.045 Hemoglobin (g/dl), median (range) (n = 117) 8.2 (3.914.9) 8.5 (4.613.7) 8.1 (3.914.9) 0.133 Platelet count (109/l), median (range) (n = 117) 55 (5570) 70 (5288) 52 (7570) 0.033 PB blast, median % (range) (n = 103) 29 (0100) 35.5 (094) 25 (0100) 0.149 BM blast, median % (range) (n = 111) 52 (7.3100) 61.3 (20100) 44 (7.3100) 0.189

Cytogenetic abnormalitiesComplex (3 clonal abnormalities), n (%) 106 (89.1) 32 (72.7) 74 (98.7) o0.001 Complex (4 clonal abnormalities), n (%) 90 (75.6) 22 (50.0) 68 (90.7) o0.001

Inv(3)/t(3;3), n (%) 8 (6.7) 6 (13.6) 2 (2.7) 0.050 Abn11q23, n (%) 1 (0.8) 1 (2.3) 0 (0) 0.370 Abn(17p), n (%) 21 (17.6) 2 (4.5) 19 (25.3) 0.004 t(6;9), n (%) 4 (3.4) 2 (4.5) 4 (2.7) 0.626 5/del(5q), n (%) 49 (41.2) 7 (15.9) 42 (56.0) o0.001 7/del(7q), n (%) 56 (47.1) 19 (43.2) 37 (49.3) 0.516

Abbreviations: AML, acute myeloid leukemia; BM, bone marrow; PB, peripheral blood; WBC, white blood cell count; y, years.

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Figure 1. Flow diagram of patients. CTx, chemotherapy; NR, non-remission.

were not available for assessment, 52 (46%) attained CR in response to induction therapy (Figure 1). As a postremission treatment, patients received 16 cycles of consolidation chemotherapy according to each institutions policy. Early/ hypoplastic death occurred in 12 patients (10.6%) and 49(43.4%) exhibited a refractory response to induction therapy. Finally, 43 patients underwent allo-HSCT: 33 of whom achieved CR status (32 patients achieved CR1 or CR2 status after successful induction therapy and 1 patient achieved CR1 with salvage chemotherapy after failing two cycles of induction therapy), whereas the remaining 10 patients had either relapsed or demonstrated a refractory response at the time of allo-HSCT. The median time interval between diagnosis and allo-HSCT was4.7 months (range 2.413.3 months). The type of donor was an HLA-matched sibling in 13 patients (30.2%), an HLA-matched unrelated donor in 20 (46.5%) and a haploidentical donor in 10(23.3%). As a conditioning regimen, myeloablative regimens were used for 20 patients (46.5%), and reduced intensity conditioning regimens based on udarabine was for the rest. Granulocyte-colony-stimulating factor mobilized peripheral blood stem cells in the majority of stem cell source (86.0%).

Prognostic factors for the response to induction therapy Supplementary Table 1 illustrates the response of patients to induction therapy and the affecting factors. CR rate decreased with age as a numerical variable (1-year old, P = 0.008), and the presence of 10% of cells with normal metaphase was another good prognostic factor for CR after induction therapy (P = 0.002) in univariate analysis. Older age (60 years) and secondary AML were associated with lower CR rate of 37% and 26.3%, respectively, although this was not signicant. The number of monosomies did not impact patients response to induction therapy (P = 0.758). In multivariate analysis, a younger age (P = 0.023) and the presence of 10% of cells with normal metaphase still signicantly correlated with a higher rate of CR achievement (P = 0.005). The factors associated with a higher incidence of early/hypoplastic death included the percent of cells with normal metaphase (P = 0.033) and the presence of abn(17p) (P = 0.037) (Supplementary Table 2).

Prognostic factors for survival outcomeThe median follow-up time was 39.4 months from diagnosis. The median OS and EFS were 8.1 months (95% condence interval (CI), range 6.59.8 months) and 4.6 months (95% CI, range3.16.1 months), respectively (Supplementary Table 3). The 3-year OS and EFS rates were 19.6% and 7.3%, respectively. Interestingly, previously well-known prognostic factors for AML, including a high white blood cell count at diagnosis, subtype of AML, CK and adverse cytogenetic abnormalities, with the exception of abn (17p), did not show any inuence on OS (Supplementary Table 3). Age o60 years, the achievement of CR after induction therapy, single monosomy subtype, the presence of 10% of cells with normal metaphase and the absence of abn(17p) were associated with better OS in univariate analysis. CK (4 clonal abnormalities)

tended to affect survival outcome, although this was not statistically signicant. In multivariate analysis, the achievement of CR after induction therapy, single monosomy subtype, the presence of 10% of cells with normal metaphase and the absence of abn(17p) remained independent prognostic factors for better OS (Table 2). The achievement of CR after induction therapy (Po0.001), single monosomy (P = 0.019) and the diagnosis of de novo AML (P = 0.027) signicantly correlated with higher EFS rates in multivariate analysis. Next, the positive impact of single monosomy subtype in patients without CK (4 clonal abnormalities) was analyzed, and single monosomy subtype has kept its positive prognostic impact on OS in patients without CK (P = 0.044; Figure 2a). Conversely, in the single monosomy group, CK did not impact OS (P = 0.401; Figure 2b).

The benecial effect of allo-HSCT in MK-AMLOf 52 patients achieving CR after induction therapy, 32 underwent allo-HSCT in CR; 13 (59%) of 22 patients with single monosomy and 19 (63%) of 30 patients with 2 monosomies underwent allo-

HSCT in CR. Table 3 shows the result of multivariate analyses for OS and RFS in patients who achieved CR after induction therapy. In multivariate analysis, single monosomy subtype (hazard ratio (HR): 0.314, 95% CI: 0.1350.732; P = 0.007) and allo-HSCT in CR (HR: 0.268; 95% CI: 0.0900.798; P = 0.018) were independent predictive factors for better OS (Table 3). Although allo-HSCT in CR improved survival in patients achieving CR after induction therapy (P = 0.020; Figure 3a), allo-HSCT as a salvage treatment (n = 8) did

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Table 2. Multivariate analysis of prognostic factors for OS and EFS in 119 patients with MK-AML

Overall survival Event-free survival

HR (95% CI) P-value HR (95% CI) P-value

Age (o60 years) 0.868 (0.5401.397) 0.561 0.940 (0.6091.449) 0.778 Single monosomy 0.460 (0.2740.772) 0.003 0.514 (0.2940.897) 0.019

Complex (4 clonal abnormalities) 0.879 (0.4811.607) 0.676 10% Cells with normal metaphase 0.511 (0.3110.841) 0.008 0.692 (0.4471.071) 0.098

De novo AML 0.525 (0.2970.930) 0.027 Absence of abn(17p) 0.532 (0.3110.911) 0.022 0.708 (0.4111.219) 0.213 Achievement of CR after induction Tx 0.238 (0.1430.396) o0.001 0.264 (0.1680.416) o0.001

Abbreviations: AML, acute myeloid leukemia; CI, condence interval; CR, complete remission; EFS, event-free survival; HR, hazard ratio; MK, monosomal karyotype; OS, overall survival; Tx, therapy.

Figure 2. OS of (a) patients not having complex karyotype (4) according to monosomal karyotype subtype, and (b) patients with single monosomy according the degree of clonal abnormalities (4 versus o4).

not show survival benet compared with salvage chemotherapy (n = 12) for relapsed or refractory patients (P = 0.675; Figure 3b). In this comparison, patients with early/hypoplastic death during induction therapy were excluded.

Subgroup analysis for biologic prognostic factors of MK-AML Because allo-HSCT as postremission therapy has an important prognostic power for AML patients, we further performed subgroup analysis according to the type of postremission therapy. One patient who underwent transplantation in CR1 status after failing two cycles of induction therapy followed by salvage chemotherapy was excluded for analysis. Especially for 32 patients who received allo-HSCT in CR, univariate and multivariate analyses were performed for OS using Cox regression tests (Supplementary Table 4). The independent prognostic factor for a better OS for those was single monosomy subtype (HR: 0.273; 95% CI:0.0870.863; P = 0.027). The benecial impact of allo-HSCT in CR was not equally distributed in patients with single monosomy or 2 monosomies. The 3-year OS after allo-HSCT in CR for patients with single monosomy was 64.6%, and allo-HSCT in CR improved

OS signicantly in patients with single monosomy (P = 0.005; Figure 4a). However, in patients with 2 monosomies, no benecial impact of allo-HSCT could be demonstrated (P = 0.249;

Figure 4b). Next, another 86 patients who did not receive allo-HSCT in CR were analyzed to evaluate biological prognostic factors of MK-AML, excluding the therapeutic variable. Similar with the result of the analyses for the total 119 patients, multivariate analysis for these subgroup showed that the achievement of CR after induction therapy (P = 0.002), single monosomy subtype (P = 0.025), the presence of 10% of cells with normal metaphase (P = 0.019) and the absence of abn(17p) (P = 0.027) correlated signicantly with better OS rates (Supplementary Table 5). Patients with single monosomy showed superior OS compared with patients with 2 monosomies, irrespective of the inclusion of patients who received allo-HSCT in CR (P = 0.016 when these patients were excluded (Figure 5a) and P = 0.002 (Figure 5b) when these patients were included).

DISCUSSIONIn this study, we retrospectively analyzed MK-AML patients using a nationwide database from South Korean AML Registry to evaluate the predictive factors for better prognoses and to feature out clinical heterogeneity of patients according to the type of MK. MK-AML accounted for ~ 5.7% of Korean AML population, and was associated with lower CR rate after induction therapy and extremely poor outcomes, which is consistent with previous studies.5,7,16

Notwithstanding a dismal prognosis, multivariate analysis revealed that single monosomy, 10% cells with normal metaphase, the absence of abn(17p) and achievement of CR after induction therapy were prognostic factors for better OS in Korean MK-AML patients. Single monosomy was also a prognostic factor for better OS in patients who received allo-HSCT in CR.

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Table 3. Multivariate analysis of clinical outcome in 52 patients who achieved CR after induction therapy

Overall survival Relapse-free survival

HR (95% CI) P-value HR (95% CI) P-value

Single monosomy 0.314 (0.1350.732) 0.007 0.237 (0.0920.615) 0.003 WBC o50 109/l 0.177 (0.0500.628) 0.007

De novo AML 0.098 (0.0240.404) 0.001 Absence of abn(17p) 0.435 (0.1641.152) 0.179 Allo-HSCT in CR 0.268 (0.0900.798) 0.018 0.249 (0.0990.626) 0.003

Abbreviations: Allo-HSCT, allogeneic hematopoietic stem cell transplantation; AML, acute myeloid leukemia; CI, condence interval; CR, complete remission; HR, hazard ratio; WBC, white blood cell count.

Figure 3. KaplanMeier curves for OS (a) according to the receipt of allo-HSCT for consolidation in patients who achieved CR after induction therapy and (b) according to the receipt of allo-HSCT as salvage treatment in patients who did not achieve CR after induction therapy.

Figure 4. KaplanMeier estimate for OS according to the receipt of allo-HSCT in CR for consolidation in patients who achieved CR after induction therapy and (a) have a single monosomy or (b) have 2 monosomies.

The number of monosomies directly correlates with a poor prognosis in AML.57 To our knowledge, the signicance of the prognostic value of a single monosomy in MK-AML has not been reported. In our study, patients in the 2 monosomy group were older and had a higher incidence of abn(17p) and 5/del(5q), and

in multivariate analysis of PFS, single monosomy remained as a signicant factor for better PFS, whereas age, abn(17p) or 5/del (5q) had not a signicant impact on PFS. The tumor suppressor gene TP53, located in the commonly deleted region, 17p13, is associated with a higher degree of genomic complexity and very

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Figure 5. KaplanMeier estimate for OS according to the number of monosomies (a) in 86 patients, except those who received allo-HSCT in CR and (b) of 119 MK-AML patients.

poor prognosis.1719 Several studies have reported that TP53 mutations were associated with del(5q) or del(17p).20,21 TP53

alterations have been described in nearly 5480% of MK-AML cases.22 A dysfunction in the TP53 pathway contributes to an increase in chromosomal instability. The presence of abn(17p) is also an adverse risk factor in AML;23,24 however, the signicance of abn(17p) in MK-AML is not clear. Middeke et al.10 reported that MKs lose their poor prognostic value in patients who have undergone allo-HSCT when those with abn(17p) or 5/del(5q) are excluded. However, Breems et al.25 reported that MK retains its notoriously adverse prognostic value and does not depend on the inclusion of AML patients with abn(17p) and 5/del(5q). In our analysis, abn(17p), not 5/del(5q), had a signicant adverse effect among MK-AML patients. The cohort of Middekes study included elderly patients with a median age of 55 years with a range of 2277 years, and the cohort of Breemss study included patients aged 1560 years. The current study also included elderly patients with a wide age range. We found that patients with abn(17p) were signicantly older than patients without abn(17p) in our cohort. Older MK-AML patients may be more affected by abn(17p) as the incidence is higher. Nevertheless, in multivariate analysis, abn(17p) still remained a signicant impact factor for better OS, whereas age did not. The differences in prognosis between MK with single monosomy and 2 monosomies could be biologically explained

by the different incidence of the TP53 mutation-associated chromosomal abnormalities in both groups. Further research has to be needed to determine which genomic alterations are mainly associated with the prognostic cytogenetic features demonstrated in this study.

In addition to a single monosomy and the absence of abn(17p), 10% of cells with normal metaphase was also important prognostic factors. The presence of 10% of cells with normal metaphase was a prognostic factor for OS and a signicant contributor to achieving CR. A higher percent of normal cells in MK-AML has been reported to be associated with longer survival.11 How residual normal metaphases translate to longer survival is unclear. We demonstrated that having 10% of cells with normal metaphase was associated with a higher rate of CR after induction therapy and longer OS. The fact that the achievement of CR is a critical factor for long-term survival in MK-AML may explain why having 10% of cells with normal metaphase was associated with longer survival.

Allo-HSCT is currently the recommended consolidation treatment for poor-risk AML.26,27 However, several studies have reported contrasting results regarding the benet of allo-HSCT in patients achieving a CR after induction therapy,7,12,13,28 and

thus more research is necessary to dene clearly the subgroups of MK-AML that would benet from allo-HSCT. Our analysis demonstrated distinct differences in survival after allo-HSCT in CR depending on the karyotypic subtype of MK, single monosomy or 2 monosomies. The benecial role of allo-HSCT in CR was identied only in patients with single monosomy, and the 3-year

OS of patients with single monosomy who received allo-HSCT in CR was 64.6% in this study. This survival outcome is comparable with the 3-year OS rate of patients without MK reported by Fang et al.13 Although it is hard to compare the results directly, MK-AML with single monosomy might need to be distinguished from the very poor-risk group.

In our study, because allo-HSCT in CR improved outcomes, we separately analyzed patients grouped by the receipt of allo-HSCT in CR to exclude the effect of the therapeutic factor in overcoming a poor prognosis. The independent prognostic factor in both groups was having a single monosomy. This result suggests that MK-AML with single monosomy may be biologically different from MK-AML with 2 monosomies and the investigation of genetic differences is necessary.

This study has several limitations, including its retrospective design and the fact that the therapeutic strategies after induction therapy were chosen at the discretion of physicians and according to each institutions policy. However, therapeutic strategies in a single nations medical system are relatively similar, and clinical variables that may affect clinical outcomes would be comparable among patient subgroups. Moreover, nationwide database, which was used for analysis in this study, was centrally collected by the Korean Society of Hematology to secure the objectivity.

In summary, although MK-AML was generally regarded as very poor-risk factor, patients with single monosomy, the absence of abn(17p) or 10% of cells with normal metaphase experienced better prognosis than expected. Allo-HSCT had benecial effect on prognosis when performed in CR status but not in relapsed/ refractory status. However, Allo-HSCT in CR was associated with superior survival rates only in patients with a single monosomy. Interestingly, for those who did not receive allo-HSCT as postremission therapy, single monosomy was also an important favorable prognostic factor. Allo-HSCT in CR should be strongly recommended to MK-AML patients with a single monosomy, and for those with 2 monosomies, more prudent treatment regimens are required. MK-AML with single monosomy might be biologically different from MK-AML with 2 monosomies, and the biological mechanism by which these cytogenetic features inuence patient prognosis should be further investigated.

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leukemia: a GOELAMS study of 186 patients with unfavorable cytogenetic abnormalities. Blood 2011; 118: 679685.17 Haferlach C, Dicker F, Herholz H, Schnittger S, Kern W, Haferlach T. Mutations of the TP53 gene in acute myeloid leukemia are strongly associated with a complex aberrant karyotype. Leukemia 2008; 22: 15391541.18 Bowen D, Groves MJ, Burnett AK, Patel Y, Allen C, Green C et al. TP53 gene mutation is frequent in patients with acute myeloid leukemia and complex karyotype, and is associated with very poor prognosis. Leukemia 2009; 23: 203206.19 Rucker FG, Schlenk RF, Bullinger L, Kayser S, Teleanu V, Kett H et al.TP53 alterations in acute myeloid leukemia with complex karyotype correlate with specic copy number alterations, monosomal karyotype, and dismal outcome. Blood 2012; 119: 21142121.20 Sebaa A, Ades L, Baran-Marzack F, Mozziconacci MJ, Penther D, Dobbelstein S et al. Incidence of 17p deletions and TP53 mutation in myelodysplastic syndrome and acute myeloid leukemia with 5q deletion. Genes Chromosomes Cancer 2012; 51: 10861092.21 Volkert S, Kohlmann A, Schnittger S, Kern W, Haferlach T, Haferlach C. Association of the type of 5q loss with complex karyotype, clonal evolution, TP53 mutation status, and prognosis in acute myeloid leukemia and myelodysplastic syndrome.Genes Chromosomes Cancer 2014; 53: 402410.22 Gaillard JB, Chiesa J, Reboul D, Arnaud A, Brun S, Donadio D et al. Monosomal karyotype routinely denes a poor prognosis subgroup in acute myeloid leukemia and is frequently associated with TP53 deletion. Leuk Lymphoma 2012; 53: 336337.23 Rollig C, Bornhauser M, Thiede C, Taube F, Kramer M, Mohr B et al. Long-term prognosis of acute myeloid leukemia according to the new genetic risk classication of the European LeukemiaNet recommendations: evaluation of the proposed reporting system. J Clin Oncol 2011; 29: 27582765.24 Seifert H, Mohr B, Thiede C, Oelschlagel U, Schakel U, Illmer T et al. The prognostic impact of 17p (p53) deletion in 2272 adults with acute myeloid leukemia.Leukemia 2009; 23: 656663.25 Breems DA, Van Putten WL, Lowenberg B. The impact of abn(17p) and monosomy -5/del(5q) on the prognostic value of the monosomal karyotype in acute myeloid leukemia. Blood 2013; 121: 30563057.26 Cornelissen JJ, van Putten WL, Verdonck LF, Theobald M, Jacky E, Daenen SM et al.Results of a HOVON/SAKK donor versus no-donor analysis of myeloablative HLA-identical sibling stem cell transplantation in rst remission acute myeloid leukemia in young and middle-aged adults: benets for whom? Blood 2007; 109: 36583666.27 Koreth J, Schlenk R, Kopecky KJ, Honda S, Sierra J, Djulbegovic BJ et al. Allogeneic stem cell transplantation for acute myeloid leukemia in rst complete remission: systematic review and meta-analysis of prospective clinical trials. JAMA 2009; 301: 23492361.28 Stelljes M, Beelen DW, Braess J, Sauerland MC, Heinecke A, Berning B et al.Allogeneic transplantation as post-remission therapy for cytogenetically high-risk acute myeloid leukemia: landmark analysis from a single prospective multicenter trial. Haematologica 2011; 96: 972979.

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CONFLICT OF INTEREST

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REFERENCES

1 Grimwade D, Hills RK, Moorman AV, Walker H, Chatters S, Goldstone AH et al.

Renement of cytogenetic classication in acute myeloid leukemia: determination of prognostic signicance of rare recurring chromosomal abnormalities among 5876 younger adult patients treated in the United Kingdom Medical Research Council trials. Blood 2010; 116: 354365.2 Mrozek K, Heerema NA, Bloomeld CD. Cytogenetics in acute leukemia. Blood Rev 2004; 18: 115136.3 Slovak ML, Kopecky KJ, Cassileth PA, Harrington DH, Theil KS, Mohamed A et al. Karyotypic analysis predicts outcome of preremission and postremission therapy in adult acute myeloid leukemia: a Southwest Oncology Group/Eastern Cooperative Oncology Group Study. Blood 2000; 96: 40754083.4 Grimwade D, Hills RK. Independent prognostic factors for AML outcome. Hematol Am Soc Hematol Educ Program 2009, 385395.5 Breems DA, Van Putten WL, De Greef GE, Van Zelderen-Bhola SL, Gerssen-Schoorl KB, Mellink CH et al. Monosomal karyotype in acute myeloid leukemia: a better indicator of poor prognosis than a complex karyotype. J Clin Oncol 2008; 26: 47914797.6 Medeiros BC, Othus M, Fang M, Roulston D, Appelbaum FR. Prognostic impact of monosomal karyotype in young adult and elderly acute myeloid leukemia: the Southwest Oncology Group (SWOG) experience. Blood 2010; 116: 22242228.7 Kayser S, Zucknick M, Dohner K, Krauter J, Kohne CH, Horst HA et al. Monosomal karyotype in adult acute myeloid leukemia: prognostic impact and outcome after different treatment strategies. Blood 2012; 119: 551558.8 Voutiadou G, Papaioannou G, Gaitatzi M, Lalayanni C, Syrigou A, Vadikoliou C et al. Monosomal karyotype in acute myeloid leukemia denes a distinct subgroup within the adverse cytogenetic risk category. Cancer Genet 2013; 206: 3236.9 Haferlach C, Alpermann T, Schnittger S, Kern W, Chromik J, Schmid C et al. Prognostic value of monosomal karyotype in comparison to complex aberrant karyotype in acute myeloid leukemia: a study on 824 cases with aberrant karyotype. Blood 2012; 119: 21222125.10 Middeke JM, Beelen D, Stadler M, Gohring G, Schlegelberger B, Baurmann H et al. Outcome of high-risk acute myeloid leukemia after allogeneic hematopoietic cell transplantation: negative impact of abnl(17p) and 5/5q. Blood 2012; 120: 25212528.11 Xie B, Othus M, Medeiros BC, Fang M, Appelbaum FR, Estey EH. Inuence of residual normal metaphases in acute myeloid leukemia patients with monosomal karyotype. Haematologica 2011; 96: 631632.12 Cornelissen JJ, Breems D, van Putten WL, Gratwohl AA, Passweg JR, Pabst T et al. Comparative analysis of the value of allogeneic hematopoietic stem-cell transplantation in acute myeloid leukemia with monosomal karyotype versus other cytogenetic risk categories. J Clin Oncol 2012; 30: 21402146.13 Fang M, Storer B, Estey E, Othus M, Zhang L, Sandmaier BM et al. Outcome of patients with acute myeloid leukemia with monosomal karyotype who undergo hematopoietic cell transplantation. Blood 2011; 118: 14901494.14 Tomonaga M. Outline and direction of revised WHO classication of Tumors of Haematopoietic and Lymphoid Tissues. Rinsho Ketsueki 2009; 50: 14011406.15 Shaffer LGSM, Campbell LF. An International System for Human Cytogenetic Nomenclature. Karger Publishers Inc: Basel, Switzerland, 2009.16 Perrot A, Luquet I, Pigneux A, Mugneret F, Delaunay J, Harousseau JL et al. Dismal prognostic value of monosomal karyotype in elderly patients with acute myeloid

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