Chronic Myelomonocytic Leukemia

Chronic myelomonocytic leukemia (CMML) is a rare type of blood cancer. Having blood cancer means that there’s a problem with how your bone marrow — the spongy tissue inside your bones — makes blood cells. With CMML, your bone marrow makes too many abnormal monocytes, a type of white blood cell. These cells can crowd out cells you need, like red blood cells, platelets and healthy white blood cells.

Doctors classify this condition as a myeloproliferative neoplasm/myelodysplastic syndrome (MPN/MDS). Here’s what this means:

• Myeloproliferative neoplasm (MPN). Your bone marrow makes too many blood cells. Too many of one type of blood cell can cause problems with how your blood works.
• Myelodysplastic syndrome (MDS). Your bone marrow makes abnormal blood cells. Instead of having mature, healthy blood cells, you may have too many immature blast cells.

CMML can range on a spectrum from slow-growing to aggressive. Your healthcare provider will explain potential treatment options that may slow its progression.

Symptoms of chronic myelomonocytic leukemia

CMML doesn’t always cause symptoms. The first sign of chronic myelomonocytic leukemia may be abnormal results on a blood test. When symptoms are noticeable, they usually develop gradually. CMML symptoms include:

• Fatigue or weakness (a sign of low red blood cells, or anemia)
• Frequent infections (a sign of low white blood cells, or neutropenia)
• Excessive nosebleeds or bruising easily (a sign of low platelets, or thrombocytopenia)
• Enlarged spleen (splenomegaly)
• Enlarged liver (hepatomegaly)
• Unexplained weight loss
• Night sweats
• Bone pain
• Fever

Chronic myelomonocytic leukemia causes

Researchers don’t know what causes CMML. But they have identified several gene changes (mutations) associated with this condition. If you’re diagnosed, you’ll likely have more than one mutation. Some of the most common ones involve the following genes (with the most common listed first):

• TET2
• SRSF2
• ASXL1
• RAS

Risk factors

Risk factors for chronic myelomonocytic leukemia include:

• Age. Your risk increases as you get older. The median age of diagnosis is between 73 and 75. A median is a midpoint. This means half of people diagnosed are younger, and half are older.
• Sex. More males are diagnosed than females.
• Cancer treatment. About 1 in 10 people who develop CMML had previous cancer treatments like chemotherapy and radiation. Healthcare providers consider the risk of future cancers when they prescribe these treatments. They only suggest them when the benefits clearly outweigh the risks.

Complications of this condition

In about 2 out of 10 cases, chronic myelomonocytic leukemia transforms into acute myeloid leukemia (AML). Ask your healthcare provider about your risk of developing AML based on your diagnosis and risk factors.

How doctors diagnose chronic myelomonocytic leukemia

Your healthcare provider will consider your symptoms and ask about your medical history. They’ll perform tests to check your blood cells. Tests may include:

• Complete blood count. A monocyte count that’s too high (monocytosis) may be a sign of CMML.
• Peripheral blood smear. Monocytes that look irregular or immature (blast cells) when viewed beneath a microscope may be a sign of CMML.
• Bone marrow biopsy. Your provider may need to take a sample of bone marrow and test it in a lab to check for abnormal monocytes.
• Genetic testing. Providers also check for gene mutations associated with other blood cancers. This can help them eliminate other conditions that involve similar symptoms and blood test results.

Staging

Healthcare providers determine how advanced CMML is (cancer staging) based on how many blast cells you have. The stages are:

• CMML-1. Less than 4 out of every 100 cells in your blood are blasts. Less than 9 out of every 100 cells in your bone marrow are blasts.
• CMML-2. Five to 19 out of every 100 cells in your blood are blasts. Ten to 19 out of every 100 cells in your bone marrow are blasts.

The stage helps your provider decide the most effective treatment.

How is chronic myelomonocytic leukemia treated?

First, you may need treatment to ensure you have enough healthy blood cells. You may need medications or regular blood transfusions to boost your blood cell counts. This may be a part of palliative care to help you manage symptoms.

Other treatments that target CMML directly include:

• Allogeneic stem cell transplant. This is the only treatment that can potentially cure CMML. But it’s not an option for most people. Also, it can cause life-threatening complications like graft vs. host disease.
• Chemotherapy. Chemo makes it harder for the monocytes to multiply out of control. This can provide symptom relief. Drug types include hydroxyurea and hypomethylating agents (HMA).
• Clinical trials. Your provider may recommend taking part in a clinical trial if other treatments aren’t helping. Current clinical trials are studying the effectiveness of newer CMML treatments. These include targeted therapy and immunotherapy.

When should I see my healthcare provider?

You’ll see your healthcare provider regularly (usually every one to six months). It’s important not to skip appointments. During these visits, your provider will ask about your symptoms and run blood tests. They’ll assess how your treatment is working and make adjustments as needed.

In the meantime, contact your provider if you’re experiencing unexpected or severe treatment side effects. Your provider will let you know what signs to look out for based on the treatment you’re getting.

What can I expect if I have this condition?

The median life expectancy for people diagnosed with CMML is approximately between one to three years. Again, a “median” is a midpoint. This means that half of people have a shorter lifespan and half live longer. But lots of factors shape your likely outcome, or prognosis. These include:

• Blood test results. Your blood cell counts provide clues about your prognosis. Important values include your monocyte, blast cell and platelet counts. Your hemoglobin level is another important number that your healthcare provider will monitor.
• Genetic mutations. Some mutations, like mutations in the ASXL1 gene, are associated with a worse prognosis.
• Frequency of blood transfusions. Your outcome is generally better if you don’t need repeat blood transfusions to restore your blood cells.

Your prognosis also depends on whether your condition progresses to AML. This is more likely to happen if you have CMML-2.

Is there anything I can do to feel better?

One of the best things you can do if you have CMML is to take charge of your health in every way you can. Right now, eating nutrient-rich foods and getting enough sleep are essential. Balancing activity and rest are important, too. Connecting with others living with cancer is a good way to combat feelings of isolation that can come up. Speak to a therapist with expertise in working with people diagnosed with cancer.

Cancer can make a person feel helpless, but know that you’re still in charge of your life. And there are treatments available to help.