Prognostic Impact and Concurrent Genetic Alterations of CEBPA Double Mutations in Adults with Cytogenetically Intermediate-Risk Acute Myeloid Leukemia.
Authors: Yamaguchi Shunichiro , Tokunaga Kenji , Iwanaga Eisaku , Nanri Tomoko , Shimomura Taizo , Suzushima Hitoshi , Mitsuya Hiroaki , Asou Norio 
Published: October 2019

Abstract
Abstract 2538

Aims:
Among acute myeloid leukemia (AML) patients with intermediate-risk cytogenetics, C/EBPa mutations represent a distinct disease entity with a favorable clinical outcome and is adopted in the current WHO classification of AML as a provisional disease entity in the category AML with recurrent genetic abnormalities. CEBPA encodes a transcription factor that is essential for neutrophil development. AML patients with CEBPA mutations can be separated into two subgroups with a single mutation in the CEBPA (CEBPA sm) and double mutations (CEBPA dm). Biallelic mutations consisted of an N-terminal frameshift mutation and a C-terminal inframe bZIP mutation were detected in the majority of CEBPA dm, whereas CEBPA sm occurs in either N-terminal or C-terminal regions. More recent data indicate that favorable outcome is mainly observed in AML patients with CEBPA dm but not with CEBPA sm. In addition, concurrent gene mutations may occur more frequently in AML with CEBPA sm than in CEBPA dm. In contrast, transcription factor GATA2 mutations are frequently identified in AML with CEBPA dm. In this study, we examined incidence, concurrent gene mutations and clinical significance of CEBPA dm and CEBPA sm in Japanese adults with cytogenetically intermediate-risk AML.

Methods:
To identify the prevalence and prognostic impact of CEBPA dm and CEBPA sm, we examined 111 patients with intermediate-risk AML who were mainly treated with the JALSG protocols. Age ranged from 16 to 86 years, with a median of 58.5 years. DNA was extracted from bone marrow or peripheral blood mononuclear cells at diagnosis and subjected to PCR amplification and direct sequencing of the CEBPA, FLT3, NPM1, IDH1, IDH2, DNMT3A and GATA2 genes. This study was approved by the Institutional Review Boards and informed consent was obtained from each patient according to guidelines based on the revised Declaration of Helsinki.

Results:
Of 111 cytogenetically intermediate-risk AML, we found 12 (10.8%) CEBPA dm and 7 (6.3%) CEBPA sm. In 7 CEBPA sm, one NPM1 mutation and one FLT3-ITD were detected. Two FLT 3-ITD and no concurrent mutation of NPM1 were found in CEBPA dm. No mutation in the IDH1, IDH2, DNMT3A exon 23 was identified in both patients with CEBPA sm and CEBPA dm. On the other hand, mutations in the GATA2 zinc finger domains were detected in 3 of 12 (25%) patients with CEBPA dm. No GATA2 mutations were found in 7 CEBPA sm. One of 21 patients with wild-type CEBPA (CEBPA wt) had a GATA2 mutation. Patients with CEBPA double or single mutations showed a better 5-year overall survival (OS) compared to CEBPA wt (51.3% vs 16.0%, P=0.0048). CEBPA dm AML was associated with a significant superior clinical outcome compared with CEBPA wt (5-year OS, 55.6% vs 16.0%, P=0.0025). However, no significant difference was identified between CEBPA dm and CEBPA sm AML (5-years OS, 55.6% vs 42.9%, P=0.1375) or between CEBPA sm and CEBPA wt AML (5-year OS, 42.9% vs 16.0%, P=0.4827). In addition, the presence of additional GATA2 mutations did not significantly influence the clinical outcome of AML patients with CEBPA dm.

Conclusions:
A total of 19 (17.1%) patients with cytogenetically intermediate-risk AML harbored CEBPA mutations. Our study indicates that the presence of the CEBPA dm but not CEBPA sm is associated with favorable outcome in Japanese patients with cytogenetically intermediate-risk AML.

Disclosures:
No relevant conflicts of interest to declare.