Systemic Mastocytosis: Management and Outcome. Data Analysis from the Greek Registry
Authors: Tsonis Ioannis , Kanellias Nikolaos , Lazaris Vasileios , Panayiotidis Panayiotis , Sotiropoulos Damianos , Vassilakopoulos Theodoros , Arapidou Zoi , Eleutherakis-Papaiakovou Evangelos , Boutsis Dimitrios , Galanopoulos Athanasios , Kotsianidis Ioannis , Kyrtsonis Marie-Christine , Leonidopoulou Theoni , Pangalis Gerasimos , Papaioannou Maria , Polychronopoulou Sophia , Pontikoglou Charalampos , Poulakidas Elias , Poziopoulos Christos , Repousis Panagiotis , Topalidou Maria , Vallianatou Kalliopi , Vervessou Elina , Viniou Nora-Athina , Angelopoulou Maria , Baltadakis Ioannis , Dimou Maria , Gavriilaki Eleni , Iliakis Theodoros , Symeonidis Argiris , Delibasi Sossana , Papathanassiou Maria , Marinakis Theodoros , Tsirigotis Panagiotis , Charchalakis Nikolaos , Terpos Evangelos , Pagoni Maria 
Published: October 2019

Abstract
Background and Methods: Systemic Mastocytosis (SM) is a rare haematologic malignancy characterized by the abnormal growth and accumulation of neoplastic mast cells in one or more organs. The cKIT D816V mutation is a common genetic finding in most cases. A subset of patients appears to be at increased risk for mediator release related symptoms as well as organ dysfunction, including skeletal problems such as osteoporosis, osteolytic lesions and fractures. The diversity of clinical manifestations results in both delayed diagnosis and therapeutic dilemmas. SM cases diagnosed in Greece, between 1987 and 2018, are presented. This project is included in the current activities of Myeloproliferative Neoplasm Working Party of Hellenic Society of Haematology for registry and research development. The medical files of the patients were retrospectively evaluated for disease characteristics, treatment and outcome.
Results: Overall 59 patients, median age 52.0 years, with SM were included in the study. Median time of symptoms onset to diagnosis was two years. Twenty-one patients were categorized as indolent SM (ISM), 19 as SM with an associated haematological neoplasm (SM-AHN), 18 as aggressive SM (ASM) and one with mast cell leukaemia (MCL). The main characteristics of the disease are shown in Table 1. Several haematologic neoplasms were associated with SM. Although myeloid malignancies were the most common, including MDS or MDS/MPN (n=9), CMML (n=2), AML (n=1), CML (n=1) and ET (n=1), lymphoid malignancies were also reported and included NHL (n=3), HL (n=1) and B-ALL (n=1). SM and the AHN were diagnosed simultaneously in 12 cases. AHN diagnosis preceded the diagnosis of SM in 4 cases (median time: 22 months), while the opposite occurred in three cases (median time: 7.0 months). Most of the patients with ISM (16/21) did not receive any specific treatment. As far as the remaining five are concerned, one was treated with imatinib, one with hydroxyurea and the rest three received corticosteroids to control the mediators' related symptoms. One of the latter had diarrhoea without infiltration of the gastrointestinal tract and received consecutively Interferon alpha (IFNα), imatinib and corticosteroids without resolution of the syndrome. Eight patients with SM-AHN received treatment for both the SM and the co-existing haematological neoplasm, six only for the AHN, three only for SM, while three did not require treatment yet. The most common treatment for SM was IFNα (n=6), followed by imatinib (n=4), cladribine (2-CdA) (n=3) and dasatinib (n=1). Patients with ASM received either IFNα (n=8) or 2-CdA (n=5) as first line treatment. Second line treatment included imatinib (n=2), 2-CdA due to IFNα intolerance (n=1) and corticosteroids (n=2). Two patients with vertebrae fractures required surgical intervention. All patients with skeletal involvement received additionally biphosphonates. The patient with MCL received consecutively 2-CdA, chemotherapy (FLAG-Ida) and dasatinib achieving partial response and proceeded to allogeneic stem cell transplantation. He died 6 months later due to complications related to graft versus host disease. With a median follow-up of 31 months the median overall survival in the entire cohort is not reached. The median follow-up for patients with ISM and ASM is 33.5 and 18.5 months respectively, and all of them are alive with adequate disease control. Seven deaths were reported only in the group of patients with SM-AHN. Six patients died due to acute leukaemia and one due to infection, indicating that the aggressiveness of the underlying haematological malignancy is the strongest factor that affects survival in this group.
Conclusion: Systemic Mastocytosis is a rare disease with variable manifestations and outcome. Nowadays, several therapeutic modalities are available for effective disease management over time. Novel targeted therapies seem to be promising to further improve the outcome, but still early and accurate diagnosis, in accordance to WHO classification, remains important.
Table 1. Table 1.

Disclosures
Gavriilaki: European Hematology Association: Research Funding. Terpos:Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Grant, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Grant, Patents & Royalties; Genesis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Grant, Research Funding; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Grant, Patents & Royalties; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria.