How Common Is Undiagnosed Chronic Myelomonocytic Leukemia (CMML)? A Review of New Findings

How Common is CMML?

Previous estimates suggest that chronic myelomonocytic leukemia (CMML) occurs in 1-2 cases per 100,000 people.  However, because symptoms of CMML are similar to those of other conditions, it is likely underdiagnosed, and it is possible that it occurs much more frequently.  CMML can develop slowly and is often asymptomatic in its early stages, which means many people may not appear to be sick despite having a serious condition. 

Read more about navigating an invisible condition here. 

Knowing the true incidence of CMML will help deepen the understanding of its impact and accelerate research for a cure.  A recent study suggests that undiagnosed CMML could be more common than previous estimates show, especially in older adults. 

Identifying possible CMML cases through blood test criteria

Researchers looked at the National Health and Nutrition Examination Survey (NHANES) database, a survey that collects health and nutrition information from people across the U.S.  The study reviewed health data from 31,125 individuals, collected between 1999 and 2020, to estimate how many people may meet the criteria for a CMML diagnosis.    

To be classified as a possible case of CMML, a person had to meet the following criteria:

• High monocyte levels (a type of white blood cell), making up more than 10% of total white blood cells.

AND

• One or more of the following blood count changes:
• • Low hemoglobin,
  • Low neutrophils (a white blood cell type),
  • Low platelets

Focusing only on possible CMML cases 

To make sure the estimates were specific to possible CMML, researchers excluded people with other conditions that could cause similar blood changes:

• Anemia types that are inconsistent with CMML (red blood cells that are not enlarged or vitamin B12 or folate deficiency
• History of cancer or any infection in the last month prior to completing the questionnaire
• Elevated C-reactive protein (a protein produced by the liver that may indicate infection)
• Possible hyperinflammatory conditions
• Key lab data required to determine possible CMML missing

The estimated rate of undiagnosed CMML increases with age

The overall estimated rate of possible undiagnosed CMML was 44.8 per 100,000 people. When broken down by age, the numbers increase significantly as people get older.

Possible CMML cases per 100,000 people by age group: 

• Ages 18–30: 4.3
• Ages 30–40: 8.9
• Ages 40–50: 23.5
• Ages 50–60: 21.3 

The prevalence increased significantly after age 60. 

Possible CMML cases per 100,000 over age 60: 

• Ages 60–70: 28.9
• Ages 70–80: 40.8
• Age 80+: 885.3 

Who was most likely to have signs of CMML?

Among those possibly undiagnosed with CMML, 53% were male and 81% were white.  Compared to others in the study, on average, they had:

• Higher white blood cell counts
• Lower hemoglobin levels
• Lower platelet counts 

What this research means for people with CMML and providers

A diagnosis for CMML is complex and requires various tests such as bone marrow biopsy results, genetic testing, and repeat lab work to confirm findings over time.  

The findings in this study offer some view into how often CMML may go unrecognized and highlight the need for better approaches to diagnosis.  Certain blood test results may be early signs of CMML and could be worth a closer look by your healthcare provider. Identifying these patterns can help healthcare providers determine whether some individuals may benefit from additional diagnostic testing that could lead to earlier detection and improved management of CMML. 

Getting involved in real-world data efforts can also help increase our understanding of underdiagnosed blood cancers. You can contribute to research through simple surveys and medical history sharing, which could support better outcomes for others by clicking the link below.

Contribute to Real-World Research in HealthTree Cure Hub

Sources: 

Estimating the Prevalence of Possible Undiagnosed Chronic Myelomonocytic Leukemia in the General Population: An NHANES Analysis

American Cancer Society: Key Statistics About Chronic Myelomonocytic Leukemia (CMML)