Myeloproliferative neoplasms (MPNs) are a group of blood cancers including three main types: essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (MF). Because of the abnormal development of stem cells in their bone marrow, people with MPNs may have high white blood cell, red blood cell, or platelet counts. When there are too many red blood cells or platelets, problems can occur with blood flow, leading to blood clots — clumps of blood that form in the veins.
Clots occur in about 20 percent of people with MPNs overall, with an estimated 30 percent of people having thrombosis (blood clotting) before their MPN diagnosis.
Blood clots are a dangerous symptom of myeloproliferative disorders. To learn more about the risks of blood clots in MPNs, myMPNteam spoke with Dr. Gaby Hobbs, clinical director of the Leukemia Service at Massachusetts General Hospital in Boston. Dr. Hobbs also leads the hospital’s research program on MPNs.
Here, we explore what’s known about the risks of blood clots with MPNs, as well as how this symptom of MPNs may be treated.
A blood clot is also known as a thrombus (or, when referring to the medical condition blood clots cause, thrombosis). There are different types of blood clots, including deep vein thrombosis — a type of venous thrombosis that affects the veins found deep in the body — as well as various potential causes.
According to Dr. Hobbs, blood clots are a common complication of MPNs. In PV, in particular, the bone marrow makes too many red blood cells. These excess cells clump together, thickening the blood and slowing down its flow. PV can cause life-threatening vascular problems, like blood clots and bleeding. ET involves a high platelet count, which may also contribute to blood thickening and clotting.
Blood clots with MPNs can also be caused by concurrent health problems (comorbidities), particularly in older people. “Managing cardiovascular comorbidities when a patient has an MPN is really important toward preventing blood clots,” said Dr. Hobbs. “If patients have other medical comorbidities like high blood pressure, high cholesterol, diabetes, if they’re smokers, if they are overweight, [management] of that is really important. Improving our cardiovascular health also helps to prevent having blood clots and developing blood clots.”
Having an enlarged spleen (splenomegaly) can be a complication of MPNs. Treatment with splenectomy (removal of the spleen) may be required. However, people with MPNs who have undergone splenectomy may have an increased risk of thrombosis. As Dr. Hobbs explained, “Having a splenectomy or having surgery to remove the spleen can be associated with lots of complications, including blood clots in the abdomen.”
If you have an enlarged spleen from MPN, your doctor should help you weigh the benefits of this procedure and advise you on how to proceed once all risks have been considered.
Blood clots can cause an increased risk of serious health issues, especially in the cardiovascular system. “Blood clots can [cause] things like heart attacks or strokes,” warned Dr. Hobbs. [“That’s] why it’s so important to manage those conditions that can affect the arteries — like high blood pressure, high cholesterol.”
Serious problems resulting from blood clots can include:
Because clots can lead to several risks and complications, treating MPNs and preventing blood clots is especially important. “When we start therapy in patients with ET and PV, our goal is not just to normalize numbers, but to help patients not develop blood clots,” said Hobbs.
Hobbs also explained that doctors will look for previous health issues and risk factors for blood clots, including:
Your doctor or another medical specialist, such as an oncologist or hematologist, can help you find the right treatment options for MPNs, blood clots, and comorbid conditions that may put you at risk of serious health issues. The doctors will often work together to determine the right treatment plan for you, which may include medication, phlebotomy (bloodletting), and other options.
Dr. Hobbs noted that there are two first-line medication options — hydroxyurea and interferon — as well as other medications that can help improve blood counts and help prevent blood clots with MPNs.
Hydroxyurea, which Dr. Hobbs noted is the most common treatment for blood clots in MPNs, is a myelosuppressive agent. Myelosuppressive agents are a kind of anticancer drug that helps prevent blood cells from reproducing. According to Dr. Hobbs, this kind of medication is generally well-tolerated, particularly in those over the age of 60. The dosage of the medication may be adjusted throughout treatment to help bring a person’s blood count to the correct level.
For younger people with MPNs, interferon may be used. As its name suggests, interferon is a drug that interferes with the replication (production) of cells. Interferons play an important role in the treatment of MPNs.
Different types of interferon are available. “We have pegylated interferon,” said Dr. Hobbs, “which means that it’s an interferon that lasts longer, so patients only need to do one subcutaneous injection once a week. And there’s a new interferon called ropeginterferon that is making its way through the approval process in the United States, as well. [With] that one, you only have to take it once every two weeks, and it seems to be much better tolerated.”
Another important medication for managing blood clots is one that you may already have in your medicine cabinet: aspirin. Aspirin is an anticoagulant — a medication that decreases the blood’s clotting action.
“Aspirin is an important part of preventing blood clots for all patients,” noted Dr. Hobbs, except for those with MF who have a very low risk of clots.
Additional medications that your doctor may recommend for use by themselves or in combination include:
Phlebotomy is a recommended treatment for polycythemia vera. In PV, phlebotomy reduces the number of excess red blood cells by decreasing overall blood volume. This treatment involves removing small amounts of blood at regular intervals to decrease cell counts and prevent blood clots. The method has minor side effects, and it is considered the standard of care for people with PV.
“If a patient has a high risk for having a blood clot or if they have these other conditions that increase the risk of having a blood clot, managing the cardiovascular comorbidities is really important,” explained Dr. Hobbs,
If you have comorbid conditions such as high blood pressure or high cholesterol, talk to your doctor about healthy habits that may reduce your risk of clots. Exercise, a heart-healthy diet, maintaining a healthy body weight, and avoiding smoke and smoking may all help.
As one member of myMPNteam said, “From what I understand from my doctor and from reading, exercise is good for us because it keeps your blood flowing, which helps to reduce the chance of clotting.”
Clinical trials are an important part of medical research. They help develop and bring new treatments and medications to market, improve diagnostic processes, and improve quality of life for people living with conditions like MPNs.
As a researcher, Dr. Hobbs is a proponent of clinical trials. However, she wants people to understand the process and the possible risks of participating.
“I think when deciding to participate in a clinical trial, it is really important to be able to feel comfortable asking questions about what the trial is — the risks, the benefits — and to understand that participating in a clinical trial, no matter how excited your doctor may be about the clinical trial, is always voluntary. The relationship that you have with your doctor shouldn’t change whether or not you participate,” Dr. Hobbs said.
If you or a loved one have been diagnosed with an MPN, get support from people who have been there. It’s an important part of living with the disease.
“The MPN community is really special because they are a group of patients that tend to be really engaged with their health care, and there’s lots of online support groups and ways of getting information,” shared Dr. Hobbs. “I think that’s great because sometimes patients with empty hands can feel isolated … . And so having community and finding community online can be really important.”
On myMPNteam, the social network for people diagnosed with myeloproliferative neoplasms, members come together to ask questions, give advice, get support, and share their stories with others who understand life with MPNs.
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