Acute Erythroid Leukemia (AEL) Can Be Separated Into Distinct Prognostic Subsets Based On Cytogenetic and Molecular Genetic Characteristics
Authors: Grossmann Vera , Haferlach Claudia , Schnittger Susanne , Bacher Ulrike , Poetzinger Franziska , Weissmann Sandra , Roller Andreas , Eder Christiane , Fasan Annette , Zenger Melanie , Staller Marita , Kern Wolfgang , Kohlmann Alexander , Haferlach Torsten 
Published: October 2019

Abstract
Abstract 1394

Background:
Acute erythroid leukemia (AEL) is characterized by a predominant erythroid population and is comprising <5% of adult AML cases. Because of the relative rarity of AEL, few large studies have examined underlying clinical and genetic features.

Aims:
Molecular and cytogenetic characterization of AEL and identification of genes with prognostic impact.

Patients and Methods:
We studied an unselected cohort of 94 AEL patients including 32 female and 62 male cases; median age was 69.0 yrs (range: 21.3–88.3 yrs). Survival data was available in 73 cases; median survival was 15.9 months. First, chromosome banding analysis (n=94) was performed. In addition, all cases with normal karyotype (NK) were investigated by CGH arrays (n=32) (Human CGH 12×270K Whole-Genome Tiling Array, Roche NimbleGen, Madison, WI). Further, mutation screening for ASXL1 (n=87), CEBPA (n=94), DNMT3A (n=94), FLT3 (both internal tandem duplication (ITD) (n=93), and tyrosine-kinase domain (TKD) mutations (n=85)), IDH1 (n=93), IDH2 (n=65), NRAS (n=91), KRAS (n=93), MLL-PTD (n=79), NPM1 (n=94), RUNX1 (n=94), TP53 (n=94), and WT1 (n=90) was performed by 454 amplicon deep-sequencing (Roche, Branford, CT), Sanger sequencing or melting curve analyses. CGH array data analysis was performed using Nexus Copy Number 6.0 (BioDiscovery Inc, El Segundo, CA).

Results:
Cytogenetic data was available for all cases: 48 cases (51.1%) presented an intermediate-risk and 46 (48.9%) cases an unfavorable cytogenetic category according to the MRC Classification. By CGH array analysis 30/32 cases retained a NK, whereas in two cases small aberrations were detected: case 1: deletion of the CEBPA gene, case 2: duplication 11q13.3 to 11q25 including the ATM and MLL gene.
Molecular mutations were detected in 85/94 patients (90.4%). 63.5% (54/85) of mutated patients carried one, whereas 36.5% (31/85) of cases harbored two (n=22) or more (n=9) mutations. In detail, TP53 was the most frequently mutated gene (41 cases, 43.6%). Other alterations were detected in NPM1 (15/94; 16.0%); DNMT3A (12/94; 12.8%); ASXL1 (8/87; 9.2%); MLL-PTD (7/79; 8.9%); RUNX1 (8/94; 8.5%); IDH1 (6/93; 6.5%); WT1 (5/90; 5.6%); IDH2 (3/65; 4.6%); NRAS (3/91; 3.3%); KRAS (3/93; 3.2%); FLT3-ITD (3/93, 3.2%), FLT3-TKD (3/85, 3.5%), and CEBPA (1/94). First, we were interested in any correlation with the respective karyotype and observed that NPM1, RUNX1, and WT1 mutations correlated with an intermediate-risk karyotype (NPM1: 15/48 vs 0/46, P<0.001; RUNX1: 8/48 vs 0/46, P=0.006; WT1: 5/46 vs 0/44, P=0.056), whereas TP53mut correlated with the unfavorable karyotype (38/46 vs 3/48, P<0.001). Within the cytogenetically adverse subset TP53mut were associated with complex karyotype (36/38 vs 2/8, P<0.001). In addition, NPM1mut correlated with lower age (56±15 vs 67±13 yrs, P=0.002), whereas mutations in ASXL1, DNMT3A, and TP53 correlated with higher age (73±4 vs 64±15, P=0.001; 71±6 vs 65±14, P=0.015; 71±8 vs 61±15, P<0.001). NPM1mut were associated with longer, and RUNX1mut and TP53mut with shorter OS (OS after 2 yrs: NPM1mut vs wt: 85.1% vs 28.3%, P=0.001; RUNX1mut vs wt: 0% vs 45.2%, P=0.007; TP53mut vs wt: 9.4% vs 61.6%, P=0.001). In the univariable Cox regression analyses mutations in NPM1 (HR 0.12; P=0.004), RUNX1 (HR 3.99; P=0.013), TP53 (HR 3.19; P=0.001), age (HR 4.24, P=0.001) and adverse cytogenetics (HR 2.98, P=0.002) were significantly associated with OS. Independent prognostic factors in multivariable Cox regression analysis were: age (HR 2.6, P=0.047) and RUNX1mut (HR 6.3, P=0.006). Of note, when separating MRC intermediate from MRC adverse cases, we confirmed the longer OS of NPM1 and shorter OS of RUNX1 mutated cases in comparison to NPM1, RUNX1 wt cases (OS after 2 yrs: NPM1mut vs wt: 85.1% vs 46.3%, P=0.027; RUNX1mut vs wt: 0% vs 69.0%, P<0.001).

Conclusions:
(1) The frequency of cases with complex or other adverse karyotypes within the AEL cohort is very high (48.9%), (2) 93.7% of cases with NK also showed a NK using high-resolution CGH arrays. (3) Overall, a remarkably high mutation frequency of 90.4% was found. (4) NPM1 and RUNX1mut were exclusively detected in the cytogenetically intermediate-risk MRC, TP53 mut predominantly in the MRC adverse group and mainly in cases with complex karyotype. (5) In addition to chromosome banding analysis mutation screening of RUNX1 and NPM1 in cases with intermediate-risk karyotype should be considered for better prognostication.

Disclosures:
Grossmann: MLL Munich Leukemia Laboratory: Employment. Haferlach:MLL Munich Leukemia Laboratory: Equity Ownership. Schnittger:MLL Munich Leukemia Laboratory: Equity Ownership. Bacher:MLL Munich Leukemia Laboratory: Employment. Poetzinger:MLL Munich Leukemia Laboratory: Employment. Weissmann:MLL Munich Leukemia Laboratory: Employment. Roller:MLL Munich Leukemia Laboratory: Employment. Eder:MLL Munich Leukemia Laboratory: Employment. Fasan:MLL Munich Leukemia Laboratory: Employment. Zenger:MLL Munich Leukemia Laboratory: Employment. Staller:MLL Munich Leukemia Laboratory: Employment. Kern:MLL Munich Leukemia Laboratory: Equity Ownership. Kohlmann:MLL Munich Leukemia Laboratory: Employment. Haferlach:MLL Munich Leukemia Laboratory: Equity Ownership.