A Distinct Mutation Profile Might Contribute to the Dismal Outcome of Triple Negative Patients with Primary Myelofibrosis

Abstract Background: Recent data indicate that driver mutations are prognostically informative in patients (pts) with primary myelofibrosis (PMF). Patients with CALR type 1/like (Ty1) mutation had better survival (OS) compared with pts with CALR type 2/like (Ty2) and JAK2 V617F/ MPL W515 mutation (Tefferi A, Blood 2014; Guglielmelli P, BCJ. 2015); conversely, pts lacking any driver mutation, i.e. “triple negative”(TN), suffered from the worst survival (Rumi E, Blood 2014; Guglielmelli P, Blood 2017). Furthermore, a high molecular risk category (HMR), pointing to pts harboring at least one of ASXL1, EZH2, IDH1/2 and SRSF2 mutated genes, independently predicted for shortened survival and increased risk of leukemia (Vannucchi A, Leukemia 2013; Guglielmelli P, Leukemia 2014). Aims: To comparatively evaluate the molecular landscape of TN patients in comparison with other driver mutation categories and the possible relationships with the adverse outcome of this pts' group. Methods: The patient cohort included 680 PMF patients, diagnosed according to WHO-2016 criteria, who provided informed consent for the study. Pts were referred by 6 Italian Centers belonging to the AGIMM group. For all patients driver (JAK2, MPL, CALR) and HMR mutation status was obtained by PCR and NGS, respectively. For 201 of these patients (38 Ty1, 20 Ty2, 110 JAK2/MPL and 32 TN), extended NGS sequencing was performed using Ion Torrent platform in Florence (n=133) and a hybrid-capture NGS-CGP assay [FoundationOne heme® assay (He J et al, Blood, 2016)] in Cambridge (n=68). NGS covered a panel of 20 non-driver genes including: all coding sequence of c-KIT, TET2, RUNX1, NRAS, KRAS, DNAMT3A, IKZF1, EZH2, TP53 ; hot spot of IDH1/2 and SRSF2 and selected exons of CBL, IDH2, ASXL1, SF3B1, NFE2, SH2B3, U2AF1 and SETBP1 . The nonparametric Wilcoxon rank-sum test, Kaplan-Meier estimate of survival and log-rank test were used as appropriate. Results: Of the 680 pts included, 419 were JAK2 +(70%), 38 MPL + (5.6%), 82 TN (12.1%) and 140 CALR + (22%; 105 (75%) Ty1 and 35 (25%) Ty2). Overall, 81 pts (11.9%) progressed to AML. Death occurred in 325 pts (47.8%) after a median follow up of 4.8y. Median survival of CALR Ty1 was 17.8y vs 8.6y for CALR Ty2, 7.2y for JAK2/MPL and 2.6y for TN (P 2 HMR mutations (HR 4.1, 95%CI 3.0-5.6; P TN pts showed enrichment of SRSF2 mutations (28% vs 1% in CALR Ty1, 6% CALR Ty2, 9% JAK2/MPL ; P 2 HMR mutations were found in 27% of TN pts vs 4% Ty1, 9% Ty2, 9% JAK2/MPL (P Conclusions: These findings suggest that the worse outcome associated with Triple Negativity in PMF might be explained, at least in part, by an underlying greater mutation complexity. Disclosures Nahas: Foundation Medicine inc: Employment, Other: stockholder. He: Foundation Medicine Inc: Employment, Other: stockholder. Agarwal: Foundation Medicine Inc: Employment, Other: stockholder. Rambaldi: Novartis, Roche/Genentech, Amgen, Italfarmaco: Consultancy; Novartis, Amgen, Celgene, Sanofi: Other: Travel, Accomodations, Expenses. Mughal: Foundation Medicine Inc: Other: stockholder. Passamonti: Novartis Pharmaceuticals Corporation: Consultancy, Honoraria, Speakers Bureau. Vannucchi: Novartis: Honoraria, Speakers Bureau; Shire: Speakers Bureau.