What is polycythemia vera (PV)?

From the Guidelines

Polycythemia vera (PV) is a chronic blood cancer characterized by the overproduction of red blood cells, often accompanied by increased white blood cells and platelets, which increases the risk of blood clots, strokes, and heart attacks. This condition is typically managed with phlebotomy to maintain a hematocrit level below 45% and low-dose aspirin to reduce the risk of clotting [ 1 ]. The disease results from a JAK2 gene mutation in about 95% of cases, causing abnormal cell proliferation.

Key Management Strategies

• Phlebotomy is the primary treatment to reduce blood thickness and prevent complications [ 1 ]
• Low-dose aspirin (81-100mg daily) is recommended to reduce the risk of blood clots [ 1, 1 ]
• Cytoreductive therapy with hydroxyurea or interferon-alpha may be prescribed for higher-risk patients [ 1, 1 ]
• Patients should stay well-hydrated, avoid extreme temperatures, and maintain regular medical follow-up with complete blood counts

Recent Evidence

A recent study published in 2018 [ 1 ] found that intensive phlebotomy treatment (target hematocrit < 45%) significantly reduced the risk of cardiovascular events and major thrombotic events compared to less intensive phlebotomy treatment (target hematocrit 45-50%). This study supports the use of phlebotomy as a primary treatment for PV and highlights the importance of maintaining a low hematocrit level to prevent complications.

Quality of Life and Mortality

While polycythemia vera cannot be cured except through stem cell transplantation, proper management allows most patients to live normal lifespans with good quality of life [ 1, 1 ]. It is essential to prioritize morbidity, mortality, and quality of life when managing PV, and the current evidence supports the use of phlebotomy, low-dose aspirin, and cytoreductive therapy as effective strategies to achieve these goals. The most recent and highest quality study [ 1 ] should be prioritized when making treatment decisions, and patients should be managed aggressively to reduce their risk of cardiovascular events and improve their overall quality of life.

From the Research

Definition and Characteristics of Polycythemia Vera (PV)

• Polycythemia vera (PV) is a chronic myeloproliferative neoplasm characterized by exuberant red cell production leading to a broad range of symptoms that compromise quality of life and productivity of patients 2.
• PV is associated with an increased red blood cell mass and increased risk of thrombosis, affecting approximately 65 000 people in the US, with an annual incidence of 0.5 to 4.0 cases per 100 000 persons 3.
• Erythrocytosis (hemoglobin >16.5 mg/dL in men or >16.0 mg/dL in women) is a required diagnostic criterion, although thrombocytosis (53%) and leukocytosis (49%) are common 3.

Diagnostic Criteria and Risk Factors

• The presence of JAK2 gene variant is expected in PV, which helps distinguish PV from secondary causes of erythrocytosis, such as tobacco smoking or sleep apnea 3, 4.
• Patients with PV who are older than 60 years or have had a previous thrombotic event are considered at high risk for thrombosis 2, 4.
• Leukocytosis and a high allele burden are additional risk factors for thrombosis and myelofibrosis, respectively 4.

Symptoms and Complications

• Patients may have pruritus (33%), erythromelalgia (5.3%), transient visual changes (14%), and splenomegaly (36%) with abdominal discomfort 3.
• PV is associated with an increased risk of arterial and venous thrombosis, hemorrhage, myelofibrosis, and acute myeloid leukemia 3, 5.
• Prior to or at the time of PV diagnosis, arterial thrombosis occurred in 16% of patients and 7% had venous thrombotic events, which could involve unusual sites, such as splanchnic veins 3.

Treatment and Management

• All patients with PV should receive therapeutic phlebotomy (goal hematocrit, <45%) and low-dose aspirin (if no contraindications) 2, 3, 5, 4, 6.
• Patients who are at higher risk of thrombosis include those aged 60 years or older or with a prior thrombosis, and may benefit from cytoreductive therapy with hydroxyurea or interferon to lower thrombosis risk and decrease symptoms 2, 3, 5, 4, 6.
• Ruxolitinib is a Janus kinase inhibitor that can alleviate pruritus and decrease splenomegaly in patients who are intolerant of or resistant to hydroxyurea 2, 3, 4.