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About MPNs

 

What are MPNs?

Myeloproliferative neoplasms (MPNs) encompass a variety of stem cell disorders.

When a stem cell divides, each new cell has the potential to become another type of cell with a more specialized function, such as a red blood cell.

In all forms of MPN, something goes wrong with the stems cells in the bone marrow that leads to an overproduction or underproduction of blood cells.

There are three primary types of MPN. Each affects blood cell levels in a different way.

Polycythemia vera (PV) patients have an increased number of red blood cells.

Myelofibrosis (MF) patients have excess scar tissue in their bone marrow, impairing the ability of the marrow to produce blood cells effectively.

Essential thrombocythemia (ET) patients have an increased number of platelets (clotting cells).

There is no cure for MPNs, but with proper management most patients can live a normal life.

What does it mean?

Myeloproliferative Neoplasms (MPNs) – Pronounced “my-eh-lo-pro-lif-er-at-iv neo-plasm”

  • myelo means that the disease affects blood cells in the bone marrow.
  • proliferative means blood cells are growing or reproducing more rapidly than they should.
  • neoplasm identifies the disorder as a cancer.

Are MPNs a type of cancer or just a blood disorder?

Because MPNs are characterized by uncontrolled cell growth, most hematologists do consider them a chronic type of leukemia or cancer. The symptoms of MPN, and whether or not it will shorten life expectency, will vary depending on the type of disease and how it progresses for each patient.

Essential thrombocythemia

Essential thrombocythemia (ET), sometimes referred to as primary thrombocyctosis, is a rare bone marrow disorder characterized by the overproduction of blood platelets in the bone marrow. This can put patients at increased risk of blood clots or excessive bleeding.

  • Many ET patients have no symptoms. Others may be prone to nose bleeds and bruising or may experience headaches, burning pain in the fingertips or toes or a swelling of the spleen.
  • Most people who develop ET are diagnosed at age sixty or older and their disease remains stable over time.
  • The causes of ET are not fully understood. However, research has shown that about 50% of ET patients have a mutation in the JAK2 protein, which helps regulate blood cell production. Other gene mutations have also been implicated.
  • A minority of patients with ET progress to myelofibrosis (known as post-ET myelofibrosis) and in rare cases to acute myeloid leukemia.

About 17,000 Canadians live with ET

What does it mean?

Essential thrombocythemia – pronounced “throm-boe-sie-thee-me-uh”

  • thrombo identifies it as a condition involving platelets (thrombocytes), which are involved in blood clotting.
  • cythemia identifies it as a condition involving cells in the blood.

Treatment

There is currently no cure for ET. The main goal of treatment is to reduce the risk of complications, such as bleeding and abnormal blood clotting (thrombosis). Medications that reduce the platelet count may also be used. The role of JAK inhibitors in the treatment of ET remains investigational.

The most common treatment is daily low-dose aspirin. Other therapy options include hydroxyurea, anagrelide, interferon and busulphan – these treatments reduce the platelet count.

Learn more about treatment options.

Polycythemia Vera

Polycythemia vera (PV) is a rare disease of the bone marrow in which too many red blood cells are produced. This makes the blood thicker than normal and increases the risk of blood clots and bleeding. Clots can block blood flow through the arteries and veins, which can lead to complications such as heart attack or stroke.

Red blood cells are normally produced in the bone marrow.  With the bone marrow not functioning properly, the spleen often compensates by producing red blood cells, causing it to swell.

  • Other symptoms of PV can include headaches, blurred vision, weakness, dizziness, fatigue, skin itchiness, and burning pain in the feet.
  • The causes of PV are not known. However, nearly 95% of people with PV have a mutation in the JAK2 protein, which helps regulate blood cell production. Research is focused on the role of JAK inhibitors in helping patients with PV.
  • About 45% of PV-related deaths are associated with cardiovascular disease.
  • About 15% of people with PV develop myelofibrosis. Although rare, some patients with PV transform to acute myeloid leukemia.
  • Patients who do not suffer from other diseases (especially myelofibrosis or leukemia) have a normal to slightly reduced life expectancy.

About 17,000 Canadians live with PV

What does it mean?

Polycythemia vera – pronounced “pol-e-sigh-thee-me-uh vayr-uh”

  • cythemia identifies it as a condition involving cells in the blood.
  • poly means many. Too many red blood cells are being produced.
  • vera means that it is pimarily associated with MPN.

Treatment

There is currently no cure for PV. The goal of treatment is to reduce the number of blood cells and help to maintain normal blood counts as well as lower the risk of blood clots and other complications. Patients at low risk for complications are primarily treated with phlebotomy (bloodletting) and low-dose Aspirin.

Treatment options include:

Phlebotomy (blood letting)

Phlebotomy is the removal of a set amount of blood to control hematocrit and hemoglobin levels, primarily for patients diagnosed with PV.

Hydroxyurea

Hydroxyurea helps to reduce your white blood cell count and neutrophil count.  It also affects your hemoglobin and platelet count.

Interferon

Interferon may be used if other agents fail to control blood counts.  This treatment requires long-term administration to potentially see a reduction in counts and some symptoms.  Major side effects include flu-like symptoms, depression and fatigue.

Anagrelide

Anagrelide helps to reduce platelet count only, and is only recommended if Hydroxyurea therapy fails..  Does not help with splenomegaly, or recommended for patients with heart conditions.

Busulphan

Busulphan is a chemotherapy drug that can reduce high red blood cell count in PV patients.  Only used as a last line of therapy due to it’s potential to develop Leukemia.

Aspirin (main treatment for most PV patients)

Aspirin helps to thin your blood if you have elevated hemoglobin or platelets.  This helps to prevent blood clots (thrombosis).  Patients at low risk for complications are primarily treated with phlebotomy and low-dose aspirin.

Ruxolitinib (Jakavi®)

The JAK inhibitor Jakavi® (ruxolitinib) has been approved to treat some PV patients.  Your physician may consider Jakavi® if your disease is not well controlled with conventional cytoreductive therapy.

Learn more about treatment options.

Myelofibrosis

Myelofibrosis (MF) is the least common MPN, but the most debilitating. In this stem cell disorder, scar tissue forms in the bone marrow, impairing its ability to produce normal blood cells. This leads to severe anemia (low red blood cell count), weakness and fatigue. As the bone marrow becomes less able to create normal blood cells, blood cell production may move to the spleen and liver, causing them to swell.

  • People are not born with these mutations but acquire them during their lives. MF is rarely inherited.
  • MF may occur on its own or as a result of other types of MPN.
  • The causes of MF are not fully understood. However, research has shown that about 50% of MF patients have a mutation in the JAK2 protein, which helps regulate blood cell production. Other gene mutations have also been implicated.
  • The prognosis of MF is different for every patient. People can live for many years without having major symptoms.
  • About 20-30% of patients with MF progress to acute myeloid leukemia.

Fewer than 2,000 Canadians live with myelofibrosis

What does it mean?

Myelofibrosis – pronounced “my-ah-lo-fi-bro-sis”

  • myelo means that the disease affects blood cells in the bone marrow.
  • fibrosis relates to an excessive scarring of tissue in the bone marrow that impairs its ability to produce normal blood cells.

Treatment

There is currently no cure for MF. For patients who do not have signs of anemia, an enlarged spleen or other complications, treatment may not be necessary. Patients can remain symptom-free for years. For others the treatment goal is to reduce symptoms and improve quality of life.

Each patient with myelofibrosis is different. Treatment options range from wait and carefully watch to intensive treatment options such as allogeneic bone marrow transplantation.

Ruxolitinib (Jakavi®)

Jakavi® (also called ruxolitinib) is the first drug approved specifically to treat MF patients.  Jakavi® reduces the size of the spleen in many MF patients as well reducing some of the other symptoms of MF (night sweats, weight loss, fever, pruritis).

allogeneic stem cell transplant (bone marrow transplant)

Hematopoietic stem cell transplantation (HSCT) is also known as a bone marrow transplant.  It involves transplanting hematopoietic stem cells from a healthy donor to the patient.

allogeneic stem cell transplant is the only therapy that can cure MF.  allogeneic stem cell transplant involves using the stem cells from another donor (related or unrelated) and transplanting them into the recipient after undergoing chemotherapy (with or without radiation).  The purpose of the chemotherapy/radiation is to prepare the marrow to receive the donor cells, in order for the cells to reproduce and multiply (proliferate).  After a successful transplant blood counts will gradually improve MF symptoms will gradually reduce.

However allogeneic stem cell transplant it is not recommended for patients with lower risk disease.  Your physician may recommend a transplant if you have higher risk disease, are experiencing severe constitutional symptoms (e.g. enlarged spleen, night sweats) not controlled with other therapies or your disease is progressing.

Other treatments

Different therapies are used to treat specific symptoms of MF. Below are some common therapies used to treat specific symptoms of MF.

Anemia – (low red blood cells) may be treated with:

Blood transfusions – increase the number of red blood cells in the body

Corticosteroids These stimulate the body to make red blood cells
Androgens (such as danazol)
Erythropoiesis stimulating agents (ESAs)

An enlarged spleen (splenomegaly) may be treated with:

Ruxolitinib (Jakavi®)

Hydroxyurea – Hydroxyurea helps to reduce your white blood cell count and neutrophil count.  It also affects your hemoglobin and platelet count.

Interferon – This treatment requires long-term administration to potentially see control of blood counts.  Major side effects include flu-like symptoms, depression and fatigue.

Radiation or splenectomy – Radiation or splenectomy may be considered in severe cases.

Ruxolitinib and hydroxurea are the most common therapies for MF.

Clinical Trials

Although ruxolitinib is approved for treatment of MF, this treatment has some limitations.  For example, ruxolitinib is not suitable for some patients with a low platelet count or anemia (low hemoglobin) and some patients may experience side effects.

Clinical trials are ongoing to find other therapies for MF that do not have these disadvantages.  Your physician may recommend that a clinical trial may be suitable for you. Find out more about clinical trials.

Learn more about treatment options.

 

Related to this topic...

Get answers to Frequently Asked Questions for patients and families.

Learn more about MPNs in our Practitioner Reference.

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Watch Dr Vikas Gupta speak about Stem Cell Transplant for Myelofibrosis in the JAK2 Inhibitor Era.

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