All About Acute Monocytic Leukemia

Leukemia is a group of cancers that affect your bone marrow and cause your body to produce abnormal blood cells. Acute myeloid leukemia (AML) is the most common type of leukemia in adults and accounts for about 4 out of 5adult cases.

Acute monocytic leukemia (AML-M5) is a subtype of AML, in which at least 80 percent of the affected blood cells are a type of white blood cell called monocytes. Half of the people diagnosed with AML M5 are older than age 49.

AML-M5 causes similar symptoms in the early stages as other types of leukemia. These symptoms include:

• fatigue
• low red blood cell count
• loss of appetite

In this article, we take a look at how acute monocytic leukemia differs from other leukemias, how it’s treated, and what’s the outlook.

What is acute monocytic leukemia?

Leukemias develop in bone marrow stem cells that produce blood cells. They’re classified based on the type of blood cells affected and how quickly the disease progresses. Here’s how each main type is broken down:

• Acute leukemias: rapid onset
• Chronic leukemias: slower onset
• Myeloid leukemias: affect a type of blood stem cell called myeloid cells
• Lymphocytic leukemias: affect a type of blood stem called lymphocytes

AML is a type of leukemia that develops quickly (acute) and affects myeloid cells (myeloid).

AML-M5 is a subtype of AML that mainly affects the growth of monocytes. Monocytes have the potential to become two other types of white blood cells called macrophages and dendritic cells.

According to the National Cancer Institute, AML-M5 is diagnosed when more than 20 percent of white blood cells are abnormal or not fully developed, and more than 80 percent of the abnormal cells are monocytes or cells derived from monocytes.

Like many types of cancer, it’s not entirely clear why AML-M5 develops in some people and not others. However, it has been linked to certain genetic mutations.

In a 2019 study, genetic mutations were detected in 83.3 percentTrusted Source of people with AML-M5. The mutations FLT3-ITD and NRAS were most common.

What are the symptoms of acute monocytic leukemia?

Symptoms of AML-M5 are similar to those of many other forms of leukemia. Symptoms like fatigue or feelings of weakness are general and can have many potential causes.

Some other possible symptoms of AML-M5 include:

• bleeding disorders
• bleeding under skin or gums
• easy bruising or bleeding
• fatigue
• fever
• shortness of breath
• feeling of weakness
• loss of weight and appetite
• ankle swelling
• hypothyroidism
• swollen lymph nodes
• anemia
• low urine production
• swelling around the eyes
• progressive hearing loss
• lump under the skin

How is acute monocytic leukemia diagnosed?

Many of the symptoms of leukemia are general and can have many different causes. A healthcare professional will likely want to order a blood test to look for signs of the disease, such as a high number of abnormal white blood cells or a low blood count.

If your blood test reveals signs of leukemia, you’ll likely be referred to a doctor called a hematologist, who specializes in blood conditions.

Bone marrow biopsy

The next part of your diagnosis will likely involve a bone marrow biopsy, usually from your hip bone. During this procedure, an anesthetic will be applied to your skin. Then, the doctor will use a thin needle to remove bone marrow from the center of your hip bone.

The procedure usually takes about 20 to 30 minutes and shouldn’t be painful. Your sample will then be taken to a lab for analysis.

Other tests

Other supportive tests may be used to collect more information about the specific type of AML you have, how far it has progressed, and what the best treatment option may be.

• Spinal tap. You may be given a spinal tap to check if there are AML-M5 cells in your spinal fluid. Research from 2017 suggests that AML-M5 tends to enter your nervous system more often than other types of AML.
• Imaging tests. You may undergo imaging tests such as an X-ray, CT scan, or ultrasound to look at some of your organs and check your general health.
• Flow cytometry. Flow cytometry may help specify your condition from other leukemias and other forms of AML. It’s a laboratory test that helps identify the type of cells in your bone marrow or blood sample that are cancerous. This test looks at certain proteins on the surface of your cells.
• Cytogenetic analysis. Cytogenetic analysis is another laboratory test in which healthcare professionals search for certain genetic mutations in your cells that are common among people with AML-M5.

How is acute monocytic leukemia treated?

AML-M5 can be difficult to treat due to a limited amount of research on the best way to manage this specific type of AML.

Treatment for most forms of AML involves multidrug chemotherapy and bone marrow transplants. The amount of chemotherapy you can receive depends on factors such as your age and overall health.

Induction chemotherapy

The goal of induction chemotherapy is to kill as many cancer cells as possible. It involves taking a high dose of chemotherapy drugs that target cancer cells. Unfortunately, it also targets healthy cells in your body that divide rapidly, such as blood stem cells, skin cells, and gastrointestinal cells.

The strength of the chemotherapy you can handle may depend on your age or overall health. Chemotherapy drugs are highly toxic to your bone marrow and can cause bleeding complications, kidney failure, and other potentially serious side effects, so your doctor will run tests often to check your health.

The chemotherapy drug cytarabine and either daunorubicin or idarubicin are often used in a “7+3 regimen.” This mean you get cytarabine through an IV for 7 days, along with a small dose of one of the other medications on the first 3 days.

Here are a few other variations in the way this treatment might work:

• You may also receive cladribine.
• If you have FLT3 gene mutations, you may also orally receive a target therapy drug called midostaurin twice per day.
• If your leukemia cells have the CD33 protein, you may be given gemtuzumab ozogamicin.
• If there’s evidence of AML-M5 in your spinal fluid, drugs such as cytarabine or methotrexate, may be used.

Typically, you’ll stay in the hospital during the induction phase. If there are still signs of cancer in your body at the end of treatment, you may need another round of chemotherapy.

Consolidation therapy

After going into remission, meaning the cancer is no longer detectable, most people undergo additional chemotherapy to target any remaining undetectable cancer cells and keep the cancer from coming back.

Young and healthy individuals often undergo several cycles of high-dose cytarabine combined with bone marrow transplants. Older adults or those with other coexisting health conditions may receive lower doses of cytarabine or other chemotherapy drugs.

Bone marrow transplant

High doses of chemotherapy damage the cells in your bone marrow that produce blood cells. A bone marrow transplant replaces damaged cells with healthy ones. Two types of transplants may be performed:

• Allogeneic transplants. Bone marrow cells are drawn from a donor who is a close genetic match, such as a close relative. It’s possible to develop chronic graft-versus-host disease, in which your body sees these cells as invaders and attacks them.
• Autologous transplants. Your own bone marrow cells are removed before chemotherapy and then returned to your body after treatment.

When a suitable donor is available, allogeneic transplants are the preferred procedure.

What’s the outlook for people with acute monocytic leukemia?

The outlook for people with AML-M5 has not been clearly established. However, it is known that it often progresses quickly when left untreated.

When your body makes too much of a protein called “differentiation inhibitory factor,” it may be linked to a less promising prognosis in some people.

About 40 percent of people with AML-M5 have a mutation in their Flt3 gene, which also may be associated with a less favorable outcome.

In a 2020 study, researchers found the 5-year overall survival rate was 46 percent in a group of 132 children with AML-M5. The overall survival rate was lowest in children under 3 years old.

Researchers are continuing to study AML-M5 in clinical trials to find the best way to treat this type of leukemia. It’s likely the survival rate will continue to improve with time and new data.

Many types of leukemia that used to have high mortality rates are now very treatable, thanks to medical advancements. You can ask your doctor about clinical trials in your area, or you can search for them yourself from the U.S. National Library of Medicine.