Comprehensive molecular landscape in patients older than 80 years old diagnosed with acute myeloid leukemia: A study of the French Hauts‐de‐France AML observatory
Authors: Loïc Renaud, Olivier Nibourel, Alice Marceau‐Renaut, Bérengère Gruson, Nathalie Cambier, Pauline Lionne‐Huyghe, Bachra Choufi, Céline Rodriguez, Cécile Frimat, Isabelle Plantier, Laure Stalnikiewicz, Maxime Bemba, Céline Berthon, Jean‐Pierre Marolleau, Bruno Quesnel, Claude Preudhomme, Nicolas Duployez
Journal: American Journal of Hematology (2018)

Acute myeloid leukemia (AML) is a highly heterogeneous group of disorders in regard to genetic abnormalities, gene mutations and clinical outcome. The prognosis of adult AML is generally poor but with great discrepancies according to age which remains one of the most important prognostic factors in AML. Only 10% of older (aged ≥60 years) AML patients achieve long-term survival. While chromosomal aberrations and gene mutations are routinely used to stratify younger patients with AML, little is known about the molecular landscape in elderly patients with AML, especially because most of patients are treated outside of clinical trials. This study report the comprehensive molecular landscape of a "real world" cohort of 88 patients older than 80-years old with AML diagnosis, annotated for clinical and biological findings from the French Hauts-de-France AML observatory. All subjects were screened for 38 genes recurrently mutated in myeloid malignancies (Supporting Information). The median age at AML diagnosis was 83-years old (range 80-95). Thirty-two patients (36.4%) had a history of previous hematological malignancy or solid tumor. About a half of patients (n = 37) had cytogenetically normal (CN)-AML. Recurrent gene fusions were found in only 4 patients (RUNX1-RUNX1T1, n = 1; BCR-ABL1, n = 1; KMT2A rearrangement, n = 2). Complex karyotype and/or deletion of the short arm of the chromosome 17 [del(17p)] was found in 12 patients. The selected cohort (n = 88), based on the availability of material at AML diagnosis, was not different from the unselected patients (n = 213) for age, sex ratio, proportion of secondary AML, cytogenetics, or therapy (Supporting Information Table S1). Treatment strategies were heterogeneous: about a half received best supportive care; demethylating agents and low dose cytarabine accounted for about 15% each while only 5% of patients received intensive chemotherapy, as expected in this specific population. Median overall survival was 59 days (range 0-1672) in the whole cohort and 84 days (range 3-1561) in the selected cohort with available material (P = .613). Patients who received demethylating agents or low dose cytarabine had a better outcome than patients who received best supportive care but the interpretation of prognostic analyses remains limited because of great discrepancies in patients' characteristics and therapeutic strategies (Supporting Information Figure S1). A total of 343 mutations in 34 genes were found in 85 patients (97% of the cohort) (Supporting Information Table S2). Three patients with CN-AML had no additional mutation in the studied gene panel. The median number of mutated genes per patient was 3 (range 0-7). When grouped into functional categories (Supporting Information methods), the most common class of mutations involved genes that control DNA methylation (TET2, DNMT3A, IDH1, or IDH2) in 73% of the cohort. Importantly, 4 genes were each mutated in at least 25% of the studied cohort with TET2 mutations being by far the most common event (43% of patients) followed by SRSF2 (27%), DNMT3A (26%), and ASXL1 mutations (25%) (Figure 1 and Supporting Information Figure S2). All of them have been previously reported in age-related clonal hematopoiesis.1 Overall, 67 patients (76%) harbored at least 1 mutation and a large proportion of them (35 of 67) had 2 or more mutations in this set of 4 genes. No systematic precedence between these events was observed when considering the respective Variant allele frequencies (VAFs). Among these, only TET2 mutations were preferentially observed in patients with secondary AML (P = .001) while ASXL1 mutations were more frequent in de novo AML (P = .034) (Supporting Information Table S3). Other frequent events included RUNX1 (24%), NPM1 (19%), and TP53 mutations (17%). All cases with mutant NPM1 had at least one concomitant mutation in genes controlling DNA methylation and 7 (41%) were FLT3-ITD positive. In those cases the study of VAFs supported the fact that NPM1 mutations were acquired in founding clones bearing gene mutations involved in DNA methylation in virtually all patients (Supporting Information Figure S3). TP53-mutant AML were shown to have a significant lower number of mutations compared with other genomic subgroups (P = .016) (Supporting Information Figure S4). A large proportion of patients (43%) belonged to a heterogeneous genomic subgroup termed as "chromatin and/or RNA splicing mutations" requiring the presence at least one mutation in RUNX1, ASXL1, BCOR, STAG2, EZH2, SRSF2, SF3B1, U2AF1, ZRSR2, or KMT2A-PTD, frequently co-occurring.2 In contrast, AML with biallelic CEBPA mutations (CEBPA-dm) and AML with IDH2-R172 mutation were extremely rare in this population (1 and 2 patients, respectively). Finally, 8 patients (9%) had driver mutations (mostly TET2 and/or DNMT3A) without any class-defining lesions.2 By comparison with recently published data from Papaemmanuil et al.2 reporting comprehensive genomic profiling in younger AML patients, our data highlight a great enrichment of mutations in TET2 (P < .001), SRSF2 (P < .001), ASXL1 (P < .001), RUNX1 (P < .001), TP53 (P = .001), CBL (P = .001), BCOR (P = .002), JAK2 (P < .001), and SF3B1 (P = .011) in patients older than 80-years old (Supporting Information Figure S5). All but RUNX1 mutations have been reported to occur in age-related clonal hematopoiesis or CHIP. The same applies when we focus our data on de novo AML with the exception of JAK2 mutations. In contrast, NPM1 mutations appear less frequent in older AML patients (P = .036). The same findings were found by comparison with adult AML patients from the TCGA.3 The rate of DNMT3A mutations in our cohort does not appear statistically different from that observed in younger patients2, 3 but the pattern of mutations differs between the 2 subgroups. Indeed, while DNMT3A mutations involving the R882 codon account for about 60% of DNMT3A mutations in AML patient <60-years old2, it represents only 15% in our cohort: a rate comparable to that observed in patients with CHIP1 (Supporting Information Figure S6). AML is a disease of the elderly population. However, elderly patients are underrepresented or often excluded in current clinical trials and studies about genetic basis of the disease are lacking in this specific population of patients. When compared with previous studies in younger AML patients, those aged 80 years or more show a significant enrichment in well named "age-related mutations" which are also common in individuals with CHIP. Considering there results with those from other groups,4, 5 elderly AML is more likely to occur through the acquisition of additional molecular events in a context of prior age-related clonal hematopoiesis. Additionally, we showed that nonR882 DNMT3A mutations were overrepresented compared with younger AML patients (85% vs ≈40%) possibly reflecting 2 DNMT3A mutational patterns with different risk or time of progression. Moreover, while DNMT3A mutations are found in more than a half of patients with CHIP,1 they are found in a quarter to a third of AML patients older than 80-years old.4, 5 Together, these results suggest a limited role of DNMT3A nonR882 mutations in the risk of progression from CHIP to AML or at least a longer time to progression than for preleukemic DNMT3A-R882 or TET2 mutations. Finally, although we were not able to evaluate the impact of treatment, a better description of the molecular landscape of elderly AML is needed to improve management in this population, as no curative treatment is currently available. Indeed, some studies have shown that at least a subset of selected patients could benefit of more intensive regimens, even in octogenarian patients.4, 6 Further studies are needed to assess whether a therapeutic approach guided by molecular aberrations could improve outcome in elderly AML patients. Low dose cytarabine or even intensive chemotherapy should be preferable in fit patients with NPM1-mutated AML. On the other hand, hypomethylating agents are now widely used in this age group and remain a good option with interesting results. Lastly, considering the high frequency of mutations involving TP53, IDH1/2 or in genes encoding the RNA splicing machinery in such patients, targeted therapies available or in development may be promising. The authors thank Christophe Roumier and the Tumor Bank of the Lille University Hospital (certification NF 96900-2014/65453-1) for handling, conditioning, and storing patient samples. The work of all physicians and clinical research assistants is also acknowledged. CP, ON, and ND designed the study. ON, CR, and CF ensured data management. LR, ON, AMR, CP, and ND performed molecular analyses. BG, NC, PL, BC, IP, LS, MB, CB, JPM, and BQ enrolled patients and provided materials. LR, CP, and ND wrote the article which was approved by all the authors. Nothing to report. TABLE S1 Characteristics at AML diagnosis in patients older than 80-years old TABLE S2 Identified variants in the cohort of 88 AML patients older than 80-years old. VAFs are given by HTS. The prediction of single nucleotide variants on protein function was performed with SIFT4 and Polyphen-25 TABLE S3 Gene mutations frequencies in de novo AML vs secondary AML in patients older than 80-years old. Only mutations found in at least 5 patients are shown here FIGURE S1 Kaplan-Meier curves showing overall survival according to treatment strategies in AML patients older than 80-years old (n = 301) FIGURE S2 Distribution of identified variants in the 7 most mutated genes in AML patients older than 80-years old. Colored boxes show putative functional protein domains (mutation diagrams are done with the online MutationMapper tool: http://www.cbioportal.org). Black, green and brown dots indicate frameshift/nonsense, missense and in frame mutations, respectively FIGURE S3 Coexisting mutations in NPM1-mutant AML. A, Box plot showing the distribution of VAFs in mutated genes involved in DNA methylation (TET2, DNMT3A, IDH1, IDH2) and signaling (NRAS, KRAS, FLT3, PTPN11, CBL grouped together). B, Dot plot showing the VAFs in mutated genes for each patient with NPM1-mutant AML FIGURE S4 Number of mutated genes per patients in AML with T53 mutation (A), AML with NPM1 mutation (B), AML with mutated chromatin and/or RNA-splicing genes (C) and in the all cohort FIGURE S5 Gene mutations frequencies in AML patients older than 80-years old (pink color) compared with younger patients (blue color) reported by Papaemmanuil et al7: this study reported comprehensive sequencing in a large cohort of 1540 AML patients enrolled in 3 prospective trials, mostly aged from 18- to 60-years old (only 11% were older than 60-years old). Panel A shows frequencies for all patients included in our study. Panel B is restricted patients with de novo AML FIGURE S6 Proportion of DNMT3A mutations involving the R882 codon vs nonR882 in AML patients from (A) this study, (B) in younger AML patients from Papaemmanuil et al.,7 and (C) in individuals with CHIP from Jaiswal et al.8 Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.