Systemic mastocytosis (SM): analysis of diagnostic markers and course of the disease prediction Tomáš Kozák, John Plate, Veronika Petečuková, Olga Černá   Department of Internal Medicine and Haematology, 3rdFaculty of Medicine, Charles University and University Hospital Kralovske Vinohrady, Prague, Czech Republic.

Disclosure Travel grants: ROCHE s.r.o. Amgen s.r.o. Bayer Schering Pharma s.r.o. Member of local advisory board: Amgen s.r.o., TAKEDA s.r.o, NOVARTIS s.r.o.

Mastocytosis Paul Ehrlich 1878: Mast cells (Mastzellen), mesenchymal origin 8. decade of 20. century: MC derived from bone marrow hematopoietic progenitor cell Tefferi 2003: tissue infiltration by morphologicaly and immunophenotypically atypical mastocytes WHO 2008 and WHO 2016 revised classification of MPN & AL: mastocytosis included firmly among myeloprolipherative neoplasia (MPN)

Mastocytosis epidemiology Danish registry Incidence: 0,89/100 000 Prevalence 9,59/100 000 Indolent SM: 82% SM-AHN: 4% ASM:2% MCL: 1% SM NOS: 11% Mayo Clinic registry Indolent SM: 46% SM-AHN: 40% ASM: 12% MCL: 1% Cohen SS et al. Br J Haematol 2014;166:521-8 Lim KH et al. Blood 2009;113:5727-36

Clonality & molecular biology in SM 1. Protooncogen c-kit mutation: Asp816Val (D816V) Found in other hem. cell lines in most SM Constitutional KIT (SCF) activation 2. Very rare: FIP1L1/PDGFR Fusion protein: TK 3. Other putative protooncogen: TET 2 (25% SM), etc.

WHO classification 2008 - indolent systemic mastocytosis Cutaneous mastocytosis Systemic mastocytosis - indolent systemic mastocytosis - agressive systemic mastocytosis - systemic mastocytosis associated with clonal hematologic non-MC disease (SM-AHNMD) - mast cell leukemia Localized mastocyte tumors - mastocytic sarcoma - extracutaneous mastocytoma

WHO revised classification 2016 Cutaneous mastocytosis Systemic mastocytosis - indolent systemic mastocytosis - smoldering mastocytosis - aggressive systemic mastocytosis - systemic mastocytosis with an associated hematological neoplasia (SM-AHN) - mast cell leukemia Mast cell sarcoma (isolated focal involvement of an extracutaneous organ or tissue) -

SM – making the diagnosis Major criterium: dense infiltration of MCs (> 15 MCs/ aggregate) detected in sections of BM and/or other extracutaneous organs Minor criterium: In BM biop sections or other extracut organs >25% of MCs are spindle shaped or abnormal morphology or, of all MCs in BM aspirate films >25% are immature or atypical c-kit D816V mutation in BM (PB or other extracutaneous organ) CD2 and/or CD25 with CD117 in MCs in PB, BM or other extracutaneous organ Serum total tryptase > 20ng/ml, unless SM-AHN

SM – making the diagnosis Major criterium: dense infiltration of MCs (> 15 MCs/ aggregate) detected in sections of BM and/or other extracutaneous organs Minor criterium: In BM biop sections or other extracut organs >25% of MCs are spindle shaped or abnormal morphology or, of all MCs in BM aspirate films >25% are immature or atypical c-kit D816V mutation in BM (PB or other extracutaneous organ) CD2 and/or CD25 with CD117 in MCs in PB, BM or other extracutaneous organ Serum total tryptase > 20ng/ml, unless SM-AHN Diagnosis: Major criterium + at least 1 minor or 3 minor criteria

Staging SM: B and C findings BM biopsy showing >30% infiltration by MC (focal, dense aggregates) and/or serum total tryptase level >200 ng/ml Signs of dysplasia or myeloproliferation, in non-MC lineage(s), but insufficient criteria for definitive diagnosis of a hematopoietic neoplasm (AHN), with normal or slightly abnormal FBC. Hepatomegaly without impairment of liver function, and/or palpable splenomegaly without hypersplenism, and/or lymphadenopathy on palpation or imaging. Bone marrow dysfunction manifested by one or more cytopenia(s) (ANC <1.0x109/L, Hb <10 g/dL, or platelets <100x109/L), but no obvious nonmast cell hematopoietic malignancy. Palpable hepatomegaly with impairment of liver function, ascites, and/or portal hypertension. Skeletal involvement with large osteolytic lesions and/or pathological fractures. Palpable splenomegaly with hypersplenism. Malabsorption with weight loss due to gastrointestinal mast cell infiltrates. B C

SM by risk (C or B findings) ISM (indolent SM): low tu burden, no organ failure - Isolated BM mastocytosis Smoldering SM: tu burden higher (≥2 B findings) ASM (aggressive SM): a) (pan)cytopenia, b) hepatomegaly+ ascites , c) splenomegaly + hypersplenism, d) malabsorbtion e) large osteol. lesions or osteopenia, pathol. fractures f) life threatenning impairment of other organs due to MCs infiltration - SM with eosinofilia ± lymphadenopathy SM-AHN PDGFRα, β 1+ - SM-AML, SM-MDS, SM-MPD, SM-CMML, SM-NHL, SM-HES MCL (Mast cell leukemia): >10% MC in PB and/or > 20% MCs in BM smear MCS (Mast cell sarcoma)

HE

CD117 (KIT)

SM – clinical course Tu symptomatology: bones (osteolytsis , osteopenia, patol. fr. , but also osteosclerosis), skin: UP, GIT, hepatosplenomegaly, lymphadenopathy, involved organ failure Mediator Release Symptoms: Anaphylaxis („idiopathic“, bee, wasp...), flash, acute GIT sy, Neuropsychological deterioration SM-AHN: symptomatology made by HN (AL, NHL, MDS, MPS, etc.)

SM – risk factors ISM ASM SM-AHNMD MCL Median OS (m): 198 41 24 2 Independent risk factors: Age ≥ 65 Weight loss Hb ≤ 10.0g/dl, PLT ≤100x109/l Hypalbuminemia > 5% blasts in bone marrow Lim et al. Blood 2009

Mast cell leukemia Cca 1% of SM ≥ 20% mastocytes in BM smear & mastocytes in PB Diffuse BM infiltration (≥ 70%) Aleukemic form exists (> 10%)

SM – treatment ISM: RH1, RH2 blockers, in GIT: sodium cromoglycate (Nalcrom), leukotrien blockers, EPIPEN SOS. ISM with severe allergic episodes: IF- +- Prednison ASM: no therapeutic standard Cladribin (2-CdA): 32-65% PR, IF-: 3% PR Imatinib (80% response in c-kit D816V negat, 100% response in FIP1L1/PDGFR+) ARA-C, hydroxyurea, allogenneic SCT Dasatinib? Investigational drugs: Midostaurin, Masitinib Radiotherapy: palliative in destructive bone lesions Supportive tratment: biphosphonates MCL: 3+7, 2-CdA, early allo SCT, poor prognosis

SM – treatment ISM: H1, H2 blockers, in GIT: sodium cromoglycate (Nalcrom), EPIPEN SOS. ISM with severe allergic episodes: IF- +- Prednison ASM: no therapeutic standard Cladribin (2-CdA): 32-65% PR, IF-: 3% PR Imatinib (80% response in c-kit D816V negat, 100% response in FIP1L1/PDGFR+) ARA-C, hydroxyurea, allogenneic SCT Dasatinib? Investigational drugs: Midostaurin, Masitinib Radiotherapy: palliative in destructive bone lesions Supportive tratment: biphosphonates MCL: 3+7, 2-CdA, early ALLO SCT, poor prognosis ALLO SCT

40 patients with SM

The 40 patients with SM managed at one institution F/M 22/18 Median age 61,5 (29-87) years Median age at diagnosis 53 (25-84) years ISM in 28 (70%) patients ASM in 9 (23%) patients SM – AHNMD in 3 patients (essential thrombocythaemia and AML, NHL) Urticaria pigmentosa was present in 26 (65%) patients Severe bone involvement was present in 6 (15%) patients.

Laboratory values: C-KIT, FIP1L1/PDGFRA C-KIT mutation Compartment examined positive % Bone marrow (BM) 27 22 81 Periph. blood (PB) 12 4 33 examined positive % BM & PB 8 BM posit, PB negat 5 63 BM negat, PB posit FIP1L1/PDGFRA: examined 20pts, positive: 0

Laboratory values II: serum tryptase (ST) Median 57,5 µg/l (6,03 - >200). N: <11,4 µg/l ST level in ISM: median 37,1 (6,03 - >200) µg/l, ST level in ASM: median 200 (58 - >200) µg/l High tryptase levels at time of diagnosis seems to correspond with aggressive course of the disease.

Clinical characteristics 20x ISM 1x SM-AHN Urticaria pigmentosa 3x ASM 1x SM-AHN Anaphylaxis 13x ISM 2x ASM

40 patients: management Antiallergic prophylaxis only (diet,H1,H2 blockers ,Na cromoglycate, Epipen SOS): 19 patients Interferon  (+ CS) in 1. line: 13 patients Indication anaphylaxis 3x: 1x CR, 1x # of episode decrease by 50%, 1x no response Indication ASM 9x 5x PR, rest: SD or PD Indication UP 3x: No response CR: complete remission, PR: partial remission SD: stable dsease, CS: corticosteroids

40 patients: management II cladribine (2-chlordeoxyadenosine) 3 patients with ASM v 1. line 6 patients with ASM in 2. line 1x CR, 1x PR, 1x SD 2x CR, 2x PR, 2x SD Other treatment: ARA-C, Hudroxyurea, corticosteroids. Imatinib: 0, Dasatinib: 0 OS: 37/40 patients (92,5%): 2 patients died on ASM progression, 1 patient died on AHN relaps: acute leukemia CR: complete remission, PR: partial remission, SD: stable disease

SM management update November 2017: 45 patients with SM 2 patients with aggressive ASM treated with Midostaurin in the 1. line Dose of Midostaurin: 100mg BID p.o.

SM, conclusions I SM is less common MPN but must be considered in dif. dg. in anaphylaxis with persistent high ST, especially when UP and/or organomegaly and/or lymphadenopathy and/or bone lesions are present. ISM and stable SSM without anaphylaxis: diet, antihistamines, biphosphonates (if bones ostelytic lesions) otherwise: W&W. ISM and stable SSM + repeated anaphylaxis: IF- (1 year?, dose?) + - corticosteroids. Masitinib? ASM: cladribine, IF-  + LD-ARA-C, Midostaurin SM-AHN: treatment of associated disease critical SM c-kit D816V negat, FIP1L1-PDGFRA posit. (+ - eosinophlia): imatinib mesylate.

SM, conclusions II C-kit is marker for the disease but clearly needs to be analyzed in BM for adequate sensitivity and/or use highly sensitive, allele specific, PCR assays. High tryptase levels at time of diagnosis seems to correspond with aggressive course of the disease.

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