Predicting Your Progress: Understanding CML Risk Scores

When you are first diagnosed with Chronic Myeloid Leukemia (CML), your doctor will perform a process called risk stratification. This is essentially a way of calculating how aggressive your leukemia is likely to be and how well it might respond to different treatments.

Doctors use mathematical models called risk scores to group patients into low, intermediate, or high-risk categories. Understanding these scores helps you and your care team decide which Tyrosine Kinase Inhibitor (TKI) is the best starting point for you ^[1][2].

The Evolution of Risk Scores

There are two primary scores used in CML care today: the Sokal Score and the ELTS (EUTOS Long-Term Survival) Score.

• The Sokal Score (The Historical Tool): Developed in the early 1980s, the Sokal score was created before modern TKIs existed. It was designed to predict how long patients would live in the era of traditional chemotherapy ^[1][3]. While it is still frequently used, it has a tendency to categorize more people as “high risk” than may actually be the case today ^[1][4].
• The ELTS Score (The Modern Tool): The ELTS score was specifically developed to work in the era of TKI treatment. It is now recommended by the European LeukemiaNet (ELN) as the preferred tool because it is better at predicting CML-related mortality—specifically, the risk of dying from the leukemia itself rather than other causes ^[1][5][6].

How the Scores are Calculated

Both scores use a combination of your clinical and laboratory data at the time of diagnosis. They both look at:

1. Age: Older age can sometimes be associated with different risks ^[1].
2. Spleen Size: Measured by how far the spleen extends below the ribs ^[1].
3. Platelet Count: The number of clotting cells in your blood ^[1].
4. Blast Percentage: The amount of immature white blood cells in your blood or bone marrow ^[1].

Why the ELTS Score is Superior

The ELTS score is considered more accurate for today’s patients because it recognizes that with TKI therapy, many patients will live long enough to eventually pass away from natural causes or other health conditions (like heart disease) rather than the leukemia itself ^[1][3]. By focusing on “CML-related death,” it provides a clearer picture of how the cancer is actually behaving ^[7][3].

How Risk Scores Influence Treatment

Your risk score is a key factor in choosing your first medication. See Targeted Therapy for more on treatment options.

• Low Risk: For many low-risk patients, first-generation TKIs like imatinib are an excellent choice. They are highly effective and often have fewer long-term side effects ^[8].
• High Risk: Patients categorized as high-risk by the ELTS score often benefit from starting on more potent second-generation TKIs (like dasatinib, nilotinib, or bosutinib). These drugs can drive the leukemia levels down faster and more deeply, which is critical for preventing the disease from progressing ^[7][9].

While a high-risk score may lean a doctor toward a second-generation TKI, the decision is never based on the score alone. Your doctor will also consider your overall health, such as heart or lung conditions, and your personal treatment goals ^[10][11]. For example, if you have certain cardiovascular issues, your doctor might choose imatinib even if your risk score is high, as some second-generation drugs can carry higher heart-related risks ^[12].