What is minimal residual disease (MRD) testing

Understanding Minimal Residual Disease (MRD) Testing

Minimal residual disease (MRD) testing is a highly sensitive blood test that detects tiny amounts of cancer cells remaining in your body after treatment—often at levels too small to show up on imaging scans like CT or PET scans.

How It Works

Think of it this way: Standard imaging can detect tumors when they contain millions of cancer cells. MRD testing can detect as few as 1 cancer cell among 1 million normal cells. The test looks for:

• Cancer DNA fragments in the bloodstream (called "circulating tumor DNA" or ctDNA)
• Abnormal blood cells (in blood cancers like leukemia and lymphoma)
• Genetic mutations specific to your cancer

Why Doctors Use MRD Testing

According to NCCN Guidelines and ASCO recommendations, MRD testing helps doctors:

1. Assess treatment response - Determine if your current treatment is working effectively
2. Predict outcomes - Undetectable MRD often correlates with better long-term survival
3. Guide treatment decisions - Results may influence whether to continue, change, or stop treatment
4. Monitor for recurrence - Detect cancer returning earlier than traditional imaging

What Results Mean

• MRD-negative (undetectable): No cancer cells detected at the sensitivity level tested—generally a positive sign
• MRD-positive (detectable): Cancer cells are present, which may prompt treatment adjustments

Important Context

MRD testing is increasingly used in several cancers including:

• Acute leukemias (ALL, AML)
• Chronic lymphocytic leukemia (CLL)
• Multiple myeloma
• Some solid tumors (breast cancer, colorectal cancer)

However, not all cancers routinely use MRD testing yet, and its clinical significance varies by cancer type.

Questions to Ask Your Doctor

If your care team mentions MRD testing:

1. Is MRD testing recommended for my specific cancer type?
2. What will the results tell us about my treatment response?
3. How will MRD results affect my treatment plan?
4. How often will I be tested, and when will we get results?
5. What does it mean if my MRD is positive vs. negative?

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