My Signatera test is positive. What now?
A positive Signatera result means tumor DNA specific to your cancer was detected in blood, which usually indicates residual or recurrent disease before imaging shows it. The next steps are confirming the result, deciding whether imaging or additional testing is warranted now, and asking whether the finding changes treatment or only changes how closely you are watched.
What a positive result actually says
Signatera is a tumor-informed assay. A panel is built from your own tumor sequence, so a positive result means variants unique to your cancer were found in your bloodstream. It is more specific than a generic blood test, and false positives are uncommon, though no assay is perfect.
What the result does not say is where the disease is, how much there is, or how fast it is moving. Those questions need imaging, the trend across serial draws, and the clinical picture read together.
- Detection often precedes visible recurrence on scans by months
- A single positive draw is a data point; the trend across draws carries more information
- Rising values generally matter more than any one number
The decisions a positive result puts in front of you
Broadly there are three paths: repeat the test and watch closely, image now to look for a target, or change treatment. Which one fits depends on your cancer type, what treatment you have already had, whether you are in surveillance after curative-intent therapy, and whether an intervention exists that would actually be used if disease were found.
The honest tension is that in some settings, acting earlier on a blood result has clear evidence behind it, and in others it mostly moves the date you start worrying. That distinction is worth getting straight before anyone changes a plan.
What to ask your oncologist
Bring specific questions rather than the report alone.
- Is this my first detection, or is the value rising across draws?
- Does a positive result change my treatment today, or only my monitoring interval?
- Should imaging be done now, and which modality?
- If disease is confirmed, what are the options, including trials?
Related questions
Can a Signatera result be a false positive?
It is uncommon because the panel is built from your own tumor's variants, but no test is absolute. Repeat testing and correlation with imaging and clinical findings is the standard way this is handled.
Does a positive result mean the cancer is back for certain?
It strongly suggests residual or recurrent disease, but the site and extent are unknown until imaging or biopsy shows them. Some patients have detectable ctDNA well before anything is visible.
Should I switch treatment immediately?
Not automatically. Whether an earlier switch improves outcomes depends on your cancer type and setting. That is exactly the question a careful independent read is for.
Reviewed 2026-09-22 by Kim Lockheimer, PhD, DFM.