Philadelphia-negative myeloproliferative neoplasms (MPN) are frequent and chronic myeloid malignancies including Polycythemia Vera (PV), essential thrombocythemia (ET), Primary Myelofibrosis (PMF) and Prefibrotic myelofibrosis (PreMF). These MPNs are caused by the acquisition of mutations affecting activation/proliferation pathways in hematopoietic stem cells. The principal mutations are JAK2V617F, calreticulin (CALR exon 9) and MPL W515. ET or MFP/PreMF patients who do not carry one of these three mutations are declared as triple-negative (3NEG) cases even if they are real MPN cases.
These diseases are at high risk of thrombo-embolic complications and with high morbidity/mortality. This risk varies from 4 to 30% depending on MPN subtype and mutational status.
In terms of therapy, all patients with MPNs should also take daily low-dose aspirin (LDA) as first antithrombotic drug, which is particularly efficient to reduce arterial but not venous events.
Despite the association of a cytoreductive drug and LDA, thromboses still occur in 5-8% patients/year.
All these situations have been explored in biological or clinical assays. All of them could increase the bleeding risk. We should look at different ways to reduce the thrombotic incidence: Direct Oral Anticoagulants (DOAC)? In the general population, in medical or surgical contexts, DOACs have demonstrated their efficiency to prevent or cure most of the venous or arterial thrombotic events.
At the present time, DOAC can be used in cancer populations according to International Society on Thrombosis and Haemostasis (ISTH) recommendations, except in patients with cancer at high bleeding risk (gastro-intestinal or genito-urinary cancers). Unfortunately, in trials evaluating DOAC in cancer patients, most patients have solid rather than hematologic cancers (generally less than 10% of the patients, mostly lymphoma or myeloma).
In cancer patients, DOAC are also highly efficient to reduce the incidence of thrombosis (-30 to 60%), but patients are exposed to a higher hemorrhagic risk, especially in digestive cancer patients.
In the cancer population, pathophysiology of both thrombotic and hemorrhagic events may be quite different between solid cancers and MPN. If MPN patients are also considered to be cancer patients in many countries, the pathophysiology of thrombosis is quite specific (hyperviscosity, platelet abnormalities, clonality, specific cytokines…) and they are exposed to a lower risk of digestive hemorrhages. It is thus difficult to extend findings from the "general cancer population" to MPN patients.
Unfortunately, only scarce, retrospective data regarding the use of DOAC in MPNs are available data.
We were the first to publish a "real-life" study about the use, the impact, and the risks in this population. In this local retrospective study, 25 patients with MPN were treated with DOAC for a median time of 2.1 years. We observed only one thrombosis (4%) and three major hemorrhages (12%, after trauma or unprepared surgery). Furthermore, we have compared the benefit/risk balance compared to patients treated with LDA without difference.
With the increasing evidences of efficacy and tolerance of DOAC in large cohorts of patients including cancer patients, with their proven efficacy on prevention of both arterial and venous thrombotic events and because of the absence of prospective trial using these drugs in MPN patients, we propose to study their potential benefit as primary thrombotic prevention in MPN.