Triple Negative Myeloproliferative Neoplasms (MPNs) Patients Show Low MPN10 Score and Lower Grades of Bone Marrow Fibrosis
Authors: Elnahass Yasser , Mahmoud Hossam K , Mattar Mervat , Fahmy Omar , Samra Mohamed A. , Abdelfattah Rafaat MS , Fahmy Hala , Abdelhameed Ahmed , Elrefaey Fatma , Elleithy Hend , Elmetnawy Wafaa 
Published: October 2019

Abstract
Introduction: The vast majority ofmyeloproliferative neoplasms (MPNs) patients are characterized by a molecular genetic background and by variable symptoms reflecting disease burden that may correlate with prognosis.
Aim: To study the impact of triple negative status of driver gene mutations: Janus kinase 2 (JAK2), calreticulin (CALR) and myeloproliferative leukemia virus oncogene (MPL) on disease burden and its correlation with symptom severity (MPN10 score) and degree of bone marrow (BM) fibrosis in MPNs patients.
Patients and Methods: MPN Symptom Assessment Form Total Symptom Score (MPN-SAF TSS) was assessed as median of 10 items: fatigue, concentration, early satiety, inactivity, night sweats, itching, bone pains, abdominal discomfort, weight loss and fever. JAK2V617F and MPL W515exon 10 mutations were performed by allele-specific oligonucleotide polymerase chain reaction (ASO-PCR) while CALR exon 9 insertion/deletion was detected by high-resolution melting (HRM) curve analysis.
Results: 100 MPNs patients (54 males and 46 females): 18 polycythemia vera (PV), 41 essential thrombocythemia (ET), 24 primary myelofibrosis (PMF), 10 Post-ET/PV-myelofibrosis (post-ET/PV-MF) and 7 myelodysplastic/myeloproliferative neoplasms (MDS/MPN) were included. Median age at diagnosis was 55 years (17-75) and was lower in ET than PV and PMF patients; 44 (19-75) years vs. 56 (34-70) years and 56 (20-75) years, respectively (p=0.06). JAK2 mutation was positive in 15 (85%) PV patients, 14 (34%) ET patients, 15 (62%) PMF patients, 8(80%) post-ET/PV-MF patients and zero (0%) MDS/MPN patients (p<0.001). CALR mutation was positive in zero (0%) PV patients, 10 (24%) ET patients, 4 (17%) PMF patients, zero (0%) Post-ET/PV-MF patients and zero (0%) MDS/MPN patients (p<0.05). MPL mutation was positive in zero (0%) PV patients, 2 (5%) ET patients, 1(4%) PMF patients, zero (0%) Post ET/PV-MF patients and zero (0%) MDS/MPN patients. Twenty four/93 (26%) patients were triple negative; 15 ET (16%), 3 PV (3%), 6 PMF (6%). Median MPN10 score was 21 (4-45) in ET versus 37.5 (25-56) in PV, 54 (15-80) in PMF and 59 (45-75) in Post-ET/PV-MF (p<0.001). Median MPN10 score was 25 (10-50) in triple negative patients vs. 40 (4-80) in MPNs patients showing at least one driver mutation positivity (p<0.001). BM fibrosis was present in 6 (15%) patients with triple negative vs. 33 (85%) patients showing at least one molecular marker positivity (p=0.007). Out of 52 patients having splenomegaly; seven (13.5%) patients were triple negative vs. 45 (87%) patients with at least one gene mutation (p<0.001). Out of the 24 triple negative patients, 19 (80%), 4 (16%), 1 (3%) and 0(0%) had BM fibrosis grades 0, 1, 2 and 3 vs. 36 (52%), 7 (10%), 12 (17%), 14 (20%) out of 69 patients with at least one gene mutation, respectively (p=0.002). After a median follow-up period of 16 months (3-151), overall survival (OS) was 95%. OS in PV and ET patients was 100 % versus 83 % in PMF patients (p=0.08). OS in triple negative group was 100% versus 94% in the gene mutations group (p=0.387).
Conclusion: Driver gene mutations show an impact on disease symptoms and burden. Triple negative MPNs patients in our cohort have significantly low MPN10 score and less BM fibrosis which may indicate a more indolent disease course.
Figure 1 Figure 1. Figure 2 Figure 2.

Disclosures
No relevant conflicts of interest to declare.