Number of Mutations and Type of Prior Myeloproliferative Neoplasm Are Prognostic Factors in Acute Myeloid Leukemia Post Myeloproliferative Neoplasms
Authors: Chiche Edmond , Bonnet Sarah , Bertoli Sarah , Kuykendall Andrew T , Gastaud Lauris , Boulay Pascal , De Mas Veronique , Delabesse Eric , Marceau-Renaut Alice , Preudhomme Claude , Murati Anne , Sallman David A , Raynaud S. Dominique , Recher Christian , Vey Norbert , Cluzeau Thomas 
Published: October 2019

Abstract
BACKGROUND
Post myeloproliferative neoplasms (MPN) acute myeloid leukemia (AML) occurs respectively in 1.5%, 7.0% and 11% of patients with essential thrombocytosis (ET), polycythemia vera (PV) and primary myelofibrosis (PMF). This subgroup of AML has very poor prognosis and are often excluded from clinical trials. Therefore, only few cohorts including molecular data are available.
MATERIAL AND METHODS
We retrospectively collected data from 111 patients treated in four centers in France for post MPN-AML. Clinical, molecular and treatment information was available for all patients at AML and MPN stages. DNA was extracted from samples at diagnosis of MPN chronic phase, at diagnosis of AML phase and after induction treatment. JAK2-V617F mutations were identified by qPCR (Ipsogen® MutaQuant kit, Qiagen, Germany), MPL-W515L/K mutations were identified by PCR (Ipsogen® MutaScreen kit, Qiagen, Germany) and CALR mutations were identified by conventional sequencing (Applied Biosystems, 3500Genetic Analyzer). NGS on 36 genes using Ampliseq librairy and Ion Proton sequencing (Thermofisher, Waltham, MA, USA) were performed in 96/111 patients. Overall response rate (ORR) was defined by complete remission (CR), CR with incomplete hematologic recovery (CRi), partial remission (PR) and stable disease (SD). Overall survival (OS) was calculated from the date of AML diagnosis to the date of death or last follow-up. All statistical analyses were performed using SPSS v.22 software (IBM SPSS Statistics).
RESULTS
111 patients treated for post MPN-AML were retrospectively included in this study. Sex ratio M/F was 54%/46%. Median age at AML diagnosis was 66 years (28-89, range). Cytogenetic categories were favorable, intermediate and adverse in 2 (2%), 51 (46%) and 47 (42%) patients, respectively. 25/111 (23%) patients had a monosomal karyotype (MK). Median number of additional mutations excluding from JAK2/MPL/CALR mutations was 2 (0-6, range). The most frequent additional mutations were TP53 (23%), ASXL1 (17%), TET2 (13%), SRSF2 (10%), DNMT3A (8%), SF3B1 (8%) and RUNX1 (8%). Only 2 patients were mutated for NPM1 and 2 and 4 patients were FLT3-ITD and FLT3-TKD, respectively. Prior MPN were PV, ET and PMF in 20%, 34% and 46% of patients, respectively. First line treatment was intensive chemotherapy (IC) for 61 (55%) patients, hypomethylating agents (HMA) for 10 (9%) or other treatments including best supportive care, cytoreduction for the other ones. 24/111 (22%) underwent to ASCT. ORR was 54% (with 30/71 (42%) in CR/CRi) in patients treated by IC or HMA.
We did not identify factors predicting a higher rate of CR/CRi. OS was 12 months [6-18] and was not influenced by transplant, cytogenetic categories or by the type and allele frequencies of JAK2/CALR/MPL mutations. OS was significantly longer in the group treated with HMA as compared to IC (10 versus 46 months, respectively, p=0.006); in patients with prior PV as compared to ET or MF (26 months [0-57] versus 10 months [7-13] versus 10 months [4-16] respectively, p=0.07) and in patients with presence of additional mutations other than JAK2/CALR/MPL (5 months [0-12] versus 46 months [32-60] in 38 patients without mutation versus 58 patients with presence of at least one mutation, respectively, p=0.04). By multivariate analysis, only presence of additional mutations was predictive for OS with a hazard ratio (HR) = 0.42 [0.18-0.97] (p=0.04). Finally, we followed the VAFs of JAK2 in seven patients before and after IC. We observed in 2 patients an increase of JAK2 clone correlated with CR whereas no variation of VAFs was associated with absence of CR.
CONCLUSIONS
In conclusion, we confirmed the poor prognosis of post MPN AML. Classical AML prognostic factors were not validated in our cohort. We identified the presence of mutations other than JAK2/MPL/CALR as the main prognostic factor whereas post-PV AML appeared to do better than post-ET and post-PMF AML. The very poor result of IC with or without ASCT highlights the need to develop specific clinical trials in this subgroup of AML.

Disclosures
Kuykendall: Celgene: Honoraria; Janssen: Consultancy. Sallman:Celgene: Research Funding, Speakers Bureau. Cluzeau:CELGENE: Consultancy; MENARINI: Consultancy; JAZZ PHARMA: Consultancy.