Chronic Myelomonocytic Leukemia Overview
Like many other blood cancers, chronic myelomonocytic leukemia, also known as CMML, starts in the blood-forming cells of the bone marrow. The specific cells affected by CMML are called “monocytes,” and they belong to a group of white blood cells that identify and destroy invading micro-organisms like viruses and bacteria that can cause infection. Additionally, some types of monocytes marshal the forces of other cells in the immune system to join in the fight against infectious organisms.
When a person has chronic myelomonocytic leukemia, the monocytes don’t develop into the normal germ-fighting cells they’re supposed to be. They also multiply abnormally and crowd out healthy white blood cells as well as impair the bone marrow’s ability to make red blood cells and platelets. As a result, a person with CMML is typically prone to infection as well as weakened by anemia, a condition that refers to not having enough red blood cells to carry sufficient oxygen to vital tissues. CMML can also hinder the blood’s ability to clot. What’s more, according to the American Cancer Society, between 15% and 30% of patients with CMML go on to develop acute myeloid leukemia.
Chronic myelomonocytic leukemia is a rare disease, occurring in only 4 out of a million people, which amounts to about 1,100 people in the U.S. each year. The vast majority of these are 60 or older.
Causes and risk factors of chronic myelomonocytic leukemia
Like other forms of cancer, CMML develops because of genetic changes that cause cells to reproduce and develop abnormally. The exact cause of these genetic changes is not yet fully understood. However, in the case of chronic myelomonocytic leukemia, the genetic cell mutations appear to be acquired during a person’s lifetime rather than inherited from a biological parent. Some studies have linked certain types of radiation and chemical exposure to CMML development.
In fact, prior cancer treatment with chemotherapy has been identified as a CMML risk factor. Few other risk factors have been identified apart from sex, with about twice as many men diagnosed as women, and advanced age—the median age at the time of diagnosis is between 71 and 74 years old.
Signs and symptoms of chronic myelomonocytic leukemia
Many people with CMML never experience symptoms. For those who do, symptoms may include:
- An enlarged spleen, which can lead to a feeling of fullness after eating only a small meal
- Unintended weight loss
- Frequent infections
- Unusual susceptibility to bleeding, including nosebleeds, and bruising
- Shortness of breath
- Skin rashes
- Fatigue
Often, the first sign of chronic myelomonocytic leukemia is the presence of too many monocytes in a blood sample during routine lab testing. Some CMML patients also have immature monocytes called “monoblasts” in their blood, which is not normal. These immature cells are normally found only in bone marrow.
Diagnosing chronic myelomonocytic leukemia
A diagnosis of CMML usually begins with additional blood testing, including tests that seek to rule out other potential causes of a high monocyte count. If blood tests continue to point to CMML, the diagnosis is typically confirmed through bone marrow testing.
Bone marrow testing involves two procedures that are usually performed at the same time: aspiration and biopsy. Samples are usually taken from the back of the hip bone using a long, hollow needle. During bone marrow aspiration, a sample of bone marrow fluid is collected, while the biopsy removes a small, solid piece of bone marrow. Both samples will be sent to a lab for analysis under a microscope by a pathologist.
Generally, the pathologist will look for certain kinds of cell abnormalities, including high numbers of monocytes and low numbers of normal white blood cells, red blood cells and platelets. Tests will also measure the percentage of immature monocytes that are made by the bone marrow stem cells compared to the percentage of mature cells.
Cytogenetic tests may also be performed. This involves analyzing cells for signs of chromosome abnormalities that are common in CMML cases.
Chronic myelomonocytic leukemia treatment
If a person with CMML is a good candidate and a matched donor can be found, the most effective treatment is an allogenic stem cell transplant. Usually, the donor is a brother or sister. The procedure follows high-dosage chemotherapy to kill the cancerous cells. Unfortunately, chemotherapy can also damage normal stem cells in the bone marrow.
However, few CMML patients are considered good candidates for stem cell transplantation because people with chronic myelomonocytic leukemia are typically older adults who face a serious risk of complications if their donor’s immune cells attack the host tissue. Additionally, an autologous stem cell transplant—for which a patient’s own stem cells are harvested and put back after their bone marrow is destroyed—is typically not an option for CMML patients because their bone marrow contains a high number of abnormal stem cells.
At this time, there are no treatments other than stem cell transplantation that can put CMML into remission. Therefore, treatment is usually limited to supportive care. This may include antibiotics to treat infections, blood transfusions and prescription medication. The drug hydroxyurea, for example, can help lower monocyte counts and shrink an enlarged spleen to increase the patient’s comfort.
Seeking leukemia care at Moffitt Cancer Center
The leukemia specialists in Moffitt’s Malignant Hematology Program treat a high volume of patients, including many with rare types of blood cancer like chronic myelomonocytic leukemia. The high level of training and experience of our cancer specialists is one of the reasons that Moffitt is consistently ranked among the nation’s top hospitals for cancer care.
We also take an individualized approach to cancer diagnosis and treatment. Our multispecialty team of oncologists, pathologists and supportive care providers collaborates regularly to review each patient’s condition and progress and tailor our treatment plans to meet their specific needs.
Moreover, as the only National Cancer Institute-designated Comprehensive Cancer Center based in Florida, we provide access to clinical trials and other groundbreaking treatments that aren’t readily available to patients at many other cancer hospitals. We have also disrupted the traditional patient care model to provide new patients with access to a cancer expert within a day of their first contact, so we can start treatment as soon as possible to ensure the best outcomes.
Connect with Moffitt today by calling 1-888-663-3488 or filling out our online new patient registration form. No referral is required to visit Moffitt.