Advanced Risk Stratification and Prognosis in Systemic Mastocytosis

While almost all patients with systemic mastocytosis share the same KIT D816V mutation, the “neighborhood” of other genes around that mutation can vary significantly. Doctors use advanced risk stratification to look beyond the diagnosis and predict how the disease might behave over time ^[1][2].

(A reassuring note for Indolent SM patients: If you have been diagnosed with Indolent Systemic Mastocytosis (ISM), it is important to remember that the advanced mutations and risk scoring discussed below are relevant primarily to a small minority of patients with advanced disease. For most ISM patients, the disease will not progress, and these high-risk profiles do not apply to you ^[3].)

The S/A/R Panel: High-Risk Mutations

In addition to the primary KIT mutation, some patients develop “secondary” mutations. Researchers have identified a specific group of genes, often called the S/A/R panel, that are known to increase the risk of the disease becoming more aggressive ^[4][2].

• SRSF2, ASXL1, and RUNX1: These three genes make up the S/A/R panel. If one or more of these are mutated, it is considered a “high-molecular-risk” finding ^[4][5].
• TET2: This is another common mutation in SM. While it is frequent, it is generally considered less “high-risk” than the S/A/R group, though it still helps doctors understand the overall complexity of your case ^[2][6].

The presence of these mutations—especially if there are multiple—often suggests that the disease may progress more quickly or require more intensive therapy, such as a bone marrow transplant ^[4][7].

Prognostic Scoring Systems

To give patients a more accurate “score” for their risk, doctors use mathematical models that combine your blood work, your age, and your genetic mutations.

1. IPSM (International Prognostic Scoring System)

The IPSM is primarily used to categorize patients based on clinical factors. It looks at variables like your age, whether you have anemia (low red blood cells), and your platelet counts ^[8][9].

• Low Risk: Typically includes younger patients with healthy blood counts.
• High Risk: Includes older patients or those with signs of organ stress, such as low hemoglobin or platelets ^[8][5].

2. MARS and MAPS (Molecularly-Augmented Scores)

Newer systems like MARS (Mutation-Adjusted Risk Score) and MAPS (Mutation-Augmented Prognostic Scoring System) are considered more precise because they “add” your genetic data to the clinical factors ^[5][10].

• A patient might have healthy blood counts (low clinical risk) but have an ASXL1 mutation (high molecular risk). These scoring systems help catch those nuances to ensure the patient is monitored more closely ^[5][2].

Why Risk Stratification Matters

Understanding your risk score is not about “predicting the future” with certainty; rather, it is a tool to help you and your doctor make informed choices about your care:

• Monitoring Frequency: Patients with higher-risk scores may need more frequent blood work and bone marrow biopsies to catch any changes early ^[8][11].
• Treatment Intensity: If you have high-risk mutations, your doctor might recommend starting targeted therapies like avapritinib sooner, rather than waiting for symptoms to worsen ^[7][12].
• Transplant Planning: For patients in the highest risk categories, doctors may begin searching for a bone marrow donor early in the process as a proactive measure ^[13][14].

By integrating clinical data with molecular profiling, your care team can move away from a “one-size-fits-all” approach and toward a treatment plan tailored to the unique genetic signature of your disease ^[1][15].