Which is more sensitive for detecting recurrence: MRD testing or imaging?

• A. Imaging
• B. MRD testing
• C. Neither
• D. Both equally

Answer: (B)

Minimal residual disease (MRD) testing is more sensitive for detecting recurrence because it seeks out tiny numbers of cancer cells or cancer-derived genetic material that can remain after treatment, often well below what imaging can detect. Techniques like flow cytometry, PCR, and next-generation sequencing can identify a single malignant cell among millions of normal cells, or detect circulating tumor DNA, before those cells grow into measurable lesions or produce visible or metabolically active changes on imaging. As a result, MRD can signal relapse earlier and more precisely than imaging, enabling earlier intervention. Keep in mind MRD requires specific molecular targets and may not apply to every cancer type, and imaging remains essential for locating disease and assessing structural spread when MRD information is not available or sufficient.