Chronic myelomonocytic leukaemia – Diagnostics – Overview of Information and Clinical Research

Chronic myelomonocytic leukaemia (CMML) is a rare blood cancer that often doesn’t cause symptoms initially, making early detection challenging. Many people discover they have it only after routine blood tests reveal abnormal results. Understanding the diagnostic process and the tests involved can help patients and their families navigate this complex condition with greater confidence.

Introduction: Who Should Seek Diagnosis and When

Chronic myelomonocytic leukaemia often develops without causing noticeable symptoms at first. The condition typically comes to light during routine blood tests performed for unrelated reasons, such as general health check-ups or investigations for other medical concerns. This means many people learn they have CMML before they feel unwell, which can be both surprising and unsettling.^[1]

You should consider seeking medical evaluation if you experience certain persistent symptoms that don’t seem to improve. These include feeling unusually tired or weak over an extended period, getting infections that happen frequently or don’t respond well to treatment, or noticing unusual bleeding or bruising that seems excessive compared to minor injuries. Some people also experience unexplained weight loss, night sweats that soak through bedclothes, or discomfort in the upper left side of the abdomen due to an enlarged spleen.^[1]^[5]

It’s particularly important to see your doctor if you’re in certain risk groups. CMML primarily affects older adults, with most people diagnosed between the ages of 65 and 75. Men are more likely to develop CMML than women. Additionally, if you’ve previously received chemotherapy or radiotherapy for another type of cancer, you face a slightly higher risk of developing this condition, though most people with CMML have never had these treatments.^[1]^[5]

⚠️ Important

Don’t wait for symptoms to become severe before consulting a doctor. CMML can be present for months without causing obvious problems, but early detection allows for better monitoring and timely intervention when treatment becomes necessary. If your routine blood test shows abnormal results, particularly high monocyte counts, follow up promptly with your healthcare provider.

Diagnostic Methods for Identifying CMML

Blood Tests: The First Step

The diagnostic journey for CMML typically begins with blood tests. These tests are essential because they can detect the hallmark feature of this condition: an abnormally high number of monocytes, a specific type of white blood cell that helps fight infections. In CMML, the bone marrow produces too many monocytes, and they often don’t function properly.^[1]

A complete blood count is usually the first test performed. This measures the levels of different blood cells in your body. For CMML to be diagnosed, your monocyte count must be consistently elevated, specifically at 0.5 × 10⁹ per litre or higher, with monocytes making up at least 10% of your white blood cells. The elevation must be sustained for more than three months to distinguish CMML from temporary increases caused by infections or other conditions.^[3]^[8]

Another crucial blood test is the peripheral blood smear. In this test, a drop of your blood is spread thinly on a glass slide and examined under a microscope. Laboratory specialists look at the shape, size, and appearance of your blood cells. In CMML, monocytes may look irregular or immature. These immature cells, called blast cells, are young blood cells that haven’t fully developed. The presence of blasts helps doctors understand how advanced the condition is.^[1]^[8]

Bone Marrow Tests: Looking Deeper

While blood tests provide important clues, a bone marrow biopsy is often necessary to confirm the diagnosis. Bone marrow is the soft, spongy tissue inside your bones where blood cells are made. During this procedure, a doctor removes a small sample of bone marrow, usually from your hip bone, and sends it to a laboratory for detailed examination.^[1]

The bone marrow sample allows specialists to see what’s happening at the source of blood cell production. They can count the number of abnormal cells, check for blast cells, and look for other changes that help distinguish CMML from similar blood conditions. The percentage of blast cells in the bone marrow is particularly important because it determines the subtype of CMML you have.^[11]

Genetic and Molecular Testing

Modern diagnosis of CMML includes examining the genetic makeup of your blood and bone marrow cells. Researchers have identified specific gene changes, called mutations, that are commonly found in people with CMML. These aren’t inherited from your parents; rather, they develop during your lifetime in the cells of your bone marrow.^[1]

The most common gene mutations found in CMML affect genes with names like TET2, SRSF2, ASXL1, and RAS. Around 60% of people with CMML have mutations in the TET2 gene, about 50% have SRSF2 mutations, 40% have ASXL1 mutations, and 30% have RAS pathway mutations. Most people with CMML have more than one of these genetic changes. Identifying which mutations you have helps your doctor understand your specific type of CMML and can guide treatment decisions.^[1]^[5]^[8]

Testing for these genetic changes involves examining samples of your blood or bone marrow using advanced laboratory techniques. This process, sometimes called next generation sequencing or myeloid NGS, looks at multiple genes simultaneously to create a comprehensive picture of the genetic landscape of your condition.^[11]

Chromosome Analysis

In addition to looking at individual genes, doctors also examine the chromosomes in your blood and bone marrow cells. Chromosomes are structures inside cells that contain genetic material. Some people with CMML have changes in the structure or number of their chromosomes. This test, called cytogenetics, helps doctors understand more about your condition and can provide information about how it might progress.^[5]^[11]

Additional Tests to Rule Out Other Conditions

Because CMML can resemble other blood disorders, doctors need to ensure they’re making the correct diagnosis. They’ll check that you don’t have certain conditions that can cause similar symptoms. For example, they’ll rule out chronic myeloid leukaemia, which has a specific genetic marker called BCR-ABL1 that CMML doesn’t have. They’ll also make sure your symptoms aren’t caused by infections, inflammation, or other health problems that can temporarily increase monocyte counts.^[8]^[13]

Classification Based on Test Results

Once all the tests are complete, doctors classify CMML into subtypes based on what they’ve found. One classification system divides CMML into CMML-1 and CMML-2, depending on the percentage of blast cells in your blood and bone marrow. CMML-1 has fewer blast cells (less than 5% in blood and less than 10% in bone marrow), while CMML-2 has more (5-19% in blood or 10-19% in bone marrow).^[5]^[8]

Doctors also classify CMML based on your white blood cell count. If you have fewer than 13,000 white blood cells per microlitre of blood, you’re considered to have dysplastic CMML, which tends to develop more slowly. If you have 13,000 or more white blood cells per microlitre, you have proliferative CMML, which tends to be more aggressive and has a higher risk of transforming into acute myeloid leukaemia.^[8]^[10]

⚠️ Important

The diagnostic process for CMML can feel overwhelming with multiple tests and complex terminology. Remember that each test provides your medical team with specific information needed to understand your condition fully. Don’t hesitate to ask your doctor to explain test results in simpler terms or to repeat information you didn’t understand the first time.

Diagnostics for Clinical Trial Qualification

If you’re considering participating in a clinical trial for CMML, you’ll undergo additional diagnostic tests beyond those used for standard diagnosis. Clinical trials are research studies that test new treatments, and they have specific requirements that participants must meet to ensure the safety and accuracy of the study results.^[1]

Baseline Health Assessment

Clinical trials require a comprehensive understanding of your overall health status before you can enrol. This typically involves repeating many of the standard diagnostic tests to establish a baseline, or starting point, against which changes can be measured during the trial. You’ll likely need fresh blood tests, including a complete blood count and peripheral blood smear, even if you’ve had these tests recently. This ensures that the trial has the most current information about your condition.^[8]

A new bone marrow biopsy might also be required, particularly if significant time has passed since your last one or if the trial protocol specifically requires it. This gives researchers accurate, up-to-date information about the percentage of blast cells in your bone marrow and helps confirm that you meet the trial’s eligibility criteria.^[8]

Genetic and Molecular Profiling

Many clinical trials for CMML focus on treatments that target specific genetic mutations or molecular pathways. As a result, detailed genetic testing is often a prerequisite for participation. You may need comprehensive gene sequencing to identify all the mutations present in your blood or bone marrow cells. Some trials only accept patients with particular genetic profiles, while others may stratify participants based on their mutation patterns to see how different genetic subtypes respond to treatment.^[8]^[10]

Organ Function Tests

Clinical trials must ensure that participants can safely tolerate the experimental treatment being tested. This means you’ll undergo tests to check how well your major organs are functioning. Blood tests will assess your kidney function by measuring substances like creatinine and estimating your glomerular filtration rate. Liver function tests check enzymes and proteins that indicate how well your liver is working. These tests are crucial because many cancer treatments are processed by the liver and kidneys, and problems with these organs could make treatments unsafe.^[8]

Performance Status Evaluation

Clinical trials also evaluate your physical fitness and ability to carry out daily activities. Doctors use standardized scoring systems to rate your performance status, which helps determine whether you’re healthy enough to participate in the trial. This isn’t about athletic ability but rather about whether you can care for yourself, walk around, and manage everyday tasks. People who are very frail or spend most of their time in bed may not be eligible for some trials because the treatment might be too demanding for them.^[8]

Disease Risk Stratification

Many clinical trials use risk stratification systems to group patients based on how aggressive their CMML is likely to be. These systems consider factors like your age, blood cell counts, genetic mutations, and chromosome changes to calculate a risk score. Common risk stratification systems for CMML include the CPSS (CMML-specific Prognostic Scoring System) and CPSS-Mol (which includes molecular/genetic information). Your risk category may determine whether you’re eligible for a particular trial and which treatment arm of the study you might be assigned to.^[8]^[10]

Exclusion Criteria Testing

Clinical trials have strict rules about who cannot participate, often for safety reasons. You may need tests to confirm you don’t have conditions that would exclude you from the trial. These might include tests for active infections, screening for other cancers, heart function tests like electrocardiograms or echocardiograms, and pregnancy tests for women of childbearing age. If you’ve had recent treatments for CMML or other conditions, the trial may require a waiting period before you can enrol.^[8]

Ongoing Monitoring During Trials

Once enrolled in a clinical trial, diagnostic testing doesn’t stop. Participants undergo regular monitoring throughout the study to track how their CMML responds to treatment and to watch for side effects. This typically includes frequent blood tests, periodic bone marrow biopsies at specified time points, and repeated organ function tests. These ongoing assessments are essential for evaluating whether the experimental treatment is working and whether it’s safe.^[8]

Prognosis and Survival Rate

Prognosis

The outlook for people with chronic myelomonocytic leukaemia varies considerably depending on several factors. The type of CMML you have plays a significant role in determining how the disease might progress. People with proliferative CMML, where the white blood cell count is 13,000 or higher, tend to have a more aggressive course with faster progression and higher rates of transformation to acute myeloid leukaemia compared to those with dysplastic CMML.^[8]^[10]

The specific genetic mutations present in your cells also affect prognosis. Certain mutations, particularly in genes called ASXL1 and RUNX1, are associated with poorer outcomes. Conversely, having a TET2 mutation without an ASXL1 mutation may indicate a better response to certain treatments. The number and combination of different mutations you have can influence how quickly the disease progresses.^[5]^[8]^[10]

Chromosome abnormalities detected through cytogenetic testing also provide prognostic information. Some chromosome changes are associated with more aggressive disease, while others suggest a more stable course. Your age and overall health at diagnosis, including any other medical conditions you have, affect your ability to tolerate treatments and influence your outlook.^[8]^[13]

One of the most concerning aspects of CMML is its potential to transform into acute myeloid leukaemia (AML), a more aggressive type of blood cancer. This transformation occurs when the percentage of blast cells in the blood or bone marrow exceeds 20%. Overall, between 15% and 30% of people with CMML will experience this transformation over a period of 3 to 5 years, though the risk varies based on individual factors. People with CMML-2 (higher blast counts) and proliferative CMML face higher transformation risks than those with CMML-1 and dysplastic disease.^[1]^[3]^[8]^[10]

Survival rate

Survival rates for chronic myelomonocytic leukaemia are influenced by many of the same factors that affect prognosis. It’s important to understand that survival statistics represent averages across large groups of patients and may not reflect your individual situation, as every person’s experience with CMML is unique.^[8]

Studies indicate that approximately 10% of people with CMML-2 and around 20% of those with CMML-1 survive longer than five years after diagnosis. These figures highlight the serious nature of the condition, particularly for people with more advanced disease at diagnosis. However, these statistics combine data from people diagnosed over many years, and treatment options continue to evolve.^[17]

The median age at diagnosis is between 70 and 75 years, meaning many people with CMML are older adults who may have other health conditions that also affect survival. Younger patients, sometimes called “young CMML” patients when diagnosed before age 65, generally have different outcomes compared to older adults, though the disease remains challenging to treat regardless of age.^[8]^[10]

Risk stratification systems help doctors estimate prognosis more precisely for individual patients by considering multiple factors together, including blood counts, genetic mutations, chromosome changes, and clinical features. These systems classify patients into different risk groups, each with different expected survival times. Your doctor can explain which risk category applies to your situation and what it means for your outlook.^[8]^[10]

It’s worth noting that allogeneic stem cell transplantation remains the only treatment with the potential to cure CMML. However, because of the advanced age of most patients at diagnosis and the presence of other health conditions, only about 10% of people with CMML are suitable candidates for this intensive procedure. For the majority who cannot undergo transplantation, treatment focuses on controlling the disease, managing symptoms, and maintaining quality of life.^[8]^[10]

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