What does circulating tumor DNA (ctDNA) testing tell me about my Leukemia

Understanding Circulating Tumor DNA (ctDNA) Testing in Leukemia

I appreciate this question—ctDNA testing is an increasingly important tool in leukemia care, though I want to be transparent about what the available guidelines show.

What ctDNA Testing Does

Circulating tumor DNA (ctDNA) is genetic material from leukemia cells that's released into your bloodstream. Think of it as "cancer cell debris" floating in your blood. ctDNA testing detects and measures this material, which can tell your care team:

• How much leukemia is present in your body at a molecular level
• How your leukemia is responding to treatment — sometimes before it shows up on standard blood tests
• Whether leukemia cells are still present even when they're not visible under a microscope (called minimal residual disease or MRD)
• Early warning signs of relapse or treatment resistance

What the Current Guidelines Show

According to the NCCN Guidelines for Patients: Acute Myeloid Leukemia (2025), the guidelines discuss several molecular testing methods including:

• PCR (polymerase chain reaction) — a highly sensitive technique that can find 1 abnormal cell among more than 100,000 normal cells
• Next-generation sequencing (NGS) — which can detect mutations in detailed ways that other methods might miss
• Flow cytometry — which identifies specific cell markers

These tests are used to "learn more about your subtype of AML, to target treatment, and to determine the likely course the cancer will take."

However, the current NCCN Guidelines don't extensively detail ctDNA specifically as a standalone monitoring tool in the patient education materials. This doesn't mean it's not valuable—it means this is an area where clinical practice may be evolving faster than the published guidelines.

Why This Matters for Your Care

ctDNA testing can be particularly useful for:

• Monitoring treatment response between bone marrow biopsies
• Detecting minimal residual disease (MRD) — leukemia cells that remain after treatment but aren't visible on standard tests
• Predicting relapse risk before symptoms appear
• Guiding treatment decisions about whether to continue, change, or intensify therapy

Important Questions to Ask Your Care Team

Since ctDNA testing is becoming more common but isn't yet standard in all leukemia programs, I'd recommend asking your oncologist:

1. "Is ctDNA testing available and recommended for my specific type of leukemia?"
2. "How will ctDNA results affect my treatment plan?"
3. "How often would I have ctDNA testing, and what would the results tell us?"
4. "Are there clinical trials using ctDNA monitoring that might be appropriate for me?"
5. "How does ctDNA testing compare to other methods you're using to monitor my leukemia (like bone marrow biopsies or flow cytometry)?"

The Bottom Line

ctDNA testing represents an exciting advancement in leukemia monitoring because it can detect cancer at very low levels and potentially catch problems earlier. However, your specific situation—your leukemia subtype, your treatment plan, and your care center's capabilities—will determine whether and how this test is used for you.

This information is for educational purposes only. Always consult your healthcare team for personalized medical advice and decisions.