Management Issues and Controversies in Low-Risk Patients with Essential Thrombocythemia and Polycythemia Vera

Purpose of Review Essential thrombocythemia (ET) and polycythemia vera (PV) are the most common myeloproliferative neoplasms (MPNs). Treatment of ET and PV is based on the risk for subsequent thrombosis. High-risk patients, defined as older than 60, JAK2 V617F-positive patients, or patients with a history of prior thrombosis, merit cytoreduction to control blood counts, whereas a watchful waiting paradigm is utilized in low-risk patients. However, low-risk patients have a host of other specific management issues that arise during their disease course. This review will discuss the most common management issues specific to the care of low-risk patients, including anti-platelet therapy dosing, pregnancy, and indications for early cytoreduction. Recent Findings Although low-dose aspirin is well established in PV, its indications and dosing regimens are less clear in ET. Recent evidence has supported twice daily low-dose aspirin in ET and observation alone in very low-risk ET patients. Pregnancy is not contraindicated in MPNs, and we recommend aspirin throughout pregnancy with consideration for prophylactic postpartum anticoagulation. High phlebotomy needs, symptom burden, and extreme thrombocytosis are common reasons for initiation of cytoreduction in low-risk patients, although we typically do not start cytoreduction for an isolated high platelet count alone. Recent data has also demonstrated a potential disease-modifying effect of interferons in MPNs, with some experts now advocating the early use of interferon in low-risk patients, although more mature data is needed before practice guidelines change. We evaluate the literature to inform clinical decision-making regarding these controversies, including most recent data that has challenged the "watchful waiting" paradigm. Our discussion provides guidance on common clinical scenarios seen in low-risk ET and PV patients, who face a myriad of complex management decisions in their care.