TP53 Alterations in Acute Myeloid Leukemia with Complex Karyotype Correlate with Specific Copy Number Alterations, Monosomal Karyotype, and Dismal Outcome,

Abstract 3558

Acute myeloid leukemia with complex karyotype (CK-AML, CK+) is defined as ≥3 acquired chromosome abnormalities in the absence of recurrent genetic abnormalities (WHO 2008). CK-AML account for 10–15% of all AML and are characterized by a dismal outcome. To delineate prognostic markers in this unfavorable subgroup, we performed integrative analysis using genomic profiling (array-comparative genomic hybridization [CGH] and/or single-nucleotide polymorphism [SNP] analysis), as well as TP53 mutation screening in 234 CK-AML.

TP53 mutations were found in 141/234 (60%) CK-AML comprising 130 missense, 21 insertion/deletion, nine nonsense, and eight splice site mutations; genomic losses of TP53 were identified in 94/234 (40%). Combining these data, TP53 alterations were detected in 70% of patients, and at least 66% of these exhibited biallelic alterations. TP53 alterations (loss and/or mutation in TP53) were characterized by a higher degree of genomic complexity, as measured by total number of copy number alterations per case (mean±SD 14.30±9.41 versus 6.16±5.53, P <.0001), and by the association with specific genomic alterations, that is, monosomy 3 or losses of 3q (-3/3q-) (P=.002), -5/5q- (P<.0001), -7/7q- (P=.001), -16/16q- (P<.0001), -18/18q- (P=.001), and -20/20q- (P=.004); gains of chromosome 1 or 1p (+1/+1p) (P=.001), +11/+11q (P=.0002), +13/+13q (P =.02), and +19/+19p (P =.04); and amplifications in 11q13∼25 [amp(11)(q13∼25)]. The recently described cytogenetic category “monosomal karyotype” (MK), defined as two or more autosomal monosomies or one single autosomal monosomy in the presence of structural abnormalities, for which a prognostic impact could be demonstrated even in CK-AML, was correlated with TP53 alterations (P <.0001). Clinically, TP53^altered CK-AML patients were older (median age, 61 versus 54 years, P =.002), had lower bone marrow (BM) blast counts (median 65% versus 78%, P=. 04), and had lower complete remission (CR) rates (28% versus 50%, P =.01). For multivariable analysis, a conditional model was used with an age cut point at 60 years to address the different treatment intensities applied in the different age cohorts. In this model the only significant factors for CR achievement were TP53^altered (OR, 0.55; 95%-CI, 0.30 to 1.00; P =.05) and age (OR for a 10 years difference, 0.67; 95%-CI, 0.52 to 0.87; P =.003).

TP53^altered predicted for inferior survival; the 3-year estimated survival rates for CK+/TP53^altered and CK+/TP53^unaltered patients were as follows: event-free survival (EFS), 1% versus 13% (log-rank, P =.0007); relapse-free survival (RFS), 7% versus 30% (P =.01); and overall survival (OS), 3% versus 28% (P <.0001), respectively. Other variables predicting for inferior OS in univariable analyses were age and MK. Among the cohort of CK+/MK+ AML, TP53^altered patients had a significantly worse OS (P =.0004). Multivariable analysis (stratified for age at cut point of 60 years) revealed TP53^altered (HR, 2.43; 95%-CI, 1.56 to 3.77; P =.0001), logarithm of WBC (HR, 1.62; 95%-CI 1.17 to 2.26; P =.004), and age (HR for 10 years difference, 1.26; 95%-CI, 1.01 to 1.56, P =.04), but not MK as significant variables for OS. In addition, explorative subset analysis suggested that allogeneic hematopoietic stem-cell transplantation in first CR which was performed in 30 CK-AML did not impact outcome in TP53^altered CK-AML.

In summary, TP53 is the most frequently known altered gene in CK-AML. TP53 alterations are associated with older age, genomic complexity, specific DNA copy number alterations, MK, and dismal outcome. In multivariable analysis, TP53 alteration is the most important prognostic factor in CK-AML, outweighing all other variables, including the MK category. TP53 mutational status should be assessed in clinical trials investigating novel agents in order to identify compounds that may be effective in this subset of patients.