Medical Oncologist
Monitoring & response assessment
ctDNA Monitoring: — Can a Blood Test Predict Progression Early?
When your oncologist orders a ctDNA test, you are being asked for a blood sample that may reveal what a scan cannot yet show. The test looks for fragments of cancer DNA circulating in your bloodstream and tracks how they change over time.
Medically reviewed by Dr. Bharati Devi Gorantla, Medical Oncologist, MBBS · MD · DM (Adyar, Chennai) · ECMO · MRCP SCE (UK) · Last reviewed August 2026
- Not the same as a tumour marker — ctDNA detects actual DNA fragments shed by cancer cells; markers like CEA or CA 125 detect proteins the tumour produces — both give different information.
- The trend matters more than one result — A single number is hard to interpret. Rising, stable, or falling compared to your own baseline is what your team is watching.
- It does not replace your scan — A ctDNA result changes what your team is looking for on imaging; it does not remove the need for a scan.
- Undetectable does not mean cured — Some tumours shed very little DNA even when active, so an undetectable result does not confirm that no cancer cells remain.
17+
Cancer Specialists
on Panel
on Panel
96.9%
Breast Cancer
Survival Rate*
Survival Rate*
15,000+
Patients
Treated
Treated
4.8★
Google Rating
(800+ reviews)
(800+ reviews)
ctDNA monitoring looks for fragments of cancer DNA shed into your blood. It gives your oncologist a signal about how the tumour is behaving between scans. A rising level can suggest growth; a falling level can suggest response. ASCO and ESMO recognise it as a useful addition to imaging in certain cancers, though it does not replace scans.
What do the terms on your ctDNA report mean?
- ctDNA — circulating tumour DNA
- Fragments of DNA shed by cancer cells into the bloodstream; the test detects these fragments to track what the tumour is doing between scans. What this means for you: your blood sample carries a snapshot of tumour activity at the time it was taken.
- Liquid biopsy
- A blood test that analyses tumour-derived material without a surgical procedure; ctDNA is one of the things a liquid biopsy can measure. What this means for you: it is less invasive than a tissue sample and can be repeated at different points in your treatment.
- VAF — variant allele frequency
- The proportion of DNA fragments in your sample that carry the cancer mutation; a higher number suggests more cancer DNA is present. What this means for you: your report may show this as a percentage or decimal — the direction of change over time matters more than the number on any one test.
- MRD — molecular residual disease
- Cancer DNA still detectable in the blood after treatment has finished; a positive MRD result means some cancer DNA remains but does not always mean disease is visible on a scan. What this means for you: your oncologist will explain whether this changes your surveillance plan.
- ctDNA clearance
- The point at which cancer DNA becomes undetectable in the blood, sometimes called a molecular response; it is a positive signal but does not confirm that all cancer cells are gone. What this means for you: clearance below the test's detection limit still requires ongoing monitoring.
- Baseline
- The ctDNA level measured before treatment starts; all later results are compared against this starting value. What this means for you: without a baseline, a single result is difficult to interpret — your team is always reading results as a trend, not a fixed target.
Questions to ask when you receive a ctDNA result
- Ask whether this result is being compared against your own baseline, not a general reference range.
- Ask whether the trend is rising, stable, or falling — a number without your own trend is hard to read.
- Ask whether your scan is still planned — a ctDNA result does not replace imaging.
- Ask what change in your result would prompt a decision to review or alter your treatment.
- Tell your team about any herbal medicines, supplements, or traditional treatments you are taking.
- Keep a copy of every ctDNA result so you and your team can track the trend over time.
Meet the Specialists
17+ senior cancer specialists. One panel for your case.
Trained at AIIMS, Tata Memorial, and leading international centres. Combined 150+ years of experience. Every complex case is reviewed by 3+ of them — together.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
Surgical Oncologist
Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
Surgical Oncologist
Surgical Oncologist
Dr. Vinay Mamidala
MBBS, MS(General Surgery), M.Ch(Surgical Oncology), FMAS, FARIS(Ongoing)
Surgical Oncologist
Radiation Oncologist
Radiation Oncologist
Radiation Oncologist
Hematologist
Interventional Radiologist
Dr. Mohammed Imran
Surgical Oncologist
Dr. Vajja Sandeep Kumar
MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology
Surgical Oncologist
Want a specific doctor for your case? Mention them when booking.
Book Free ConsultationBook an appointment with our specialist
Share your name and number — we'll call you back within 30 minutes to schedule your consultation.
You do not have to work this out alone
A 45-minute consultation with a specialist who treats this every week.
ctDNA blood test versus imaging scan: what each shows
| ctDNA blood test | Imaging scan (CT / PET-CT) | |
|---|---|---|
| What it detects | Cancer DNA fragments shed into the bloodstream | Visible tumour size, location, and metabolic activity |
| How invasive | Blood draw only | CT requires radiation exposure; PET-CT also uses a radiotracer injection |
| How often it can be done | Can be repeated at most treatment visits | Usually every few months; radiation exposure limits frequency |
| When results return | Days to weeks depending on the laboratory | Usually hours to one or two days |
| Can it replace the other | No — adds information but does not replace imaging | Imaging remains the standard for measuring tumour size |
| What a positive result means | Cancer DNA detected — needs clinical context to interpret | Measurable disease visible to the radiologist |
| Where guidance stands | Better evidenced for some cancers than others — ASCO, ESMO | Standard of care across all cancer types |
What does a rising or falling ctDNA level actually mean?
A rising ctDNA level between scans can indicate that the tumour is growing or that cells are becoming resistant to treatment. It does not confirm progression on its own — your oncologist will usually confirm with imaging before any treatment decision is made.
A falling level after treatment starts is a signal that the tumour may be responding. It does not mean all cancer cells are gone, and treatment continues until your team decides otherwise.
Not all tumours shed DNA into the blood equally. Some cancers shed very little even when active, which means a negative result does not rule out disease. Your oncologist will tell you how reliable the test is for your specific cancer type.
ASCO and ESMO guidance notes that the evidence base for ctDNA monitoring is stronger in some cancers — particularly colorectal and certain lung cancers — than in others. If you are unsure why this test was ordered for you, ask which evidence supports its use in your situation.
Explore 39 more Monitoring, Resistance & Long-Term Response topics
Monitoring, Scans & Response Assessment
- Are Tumour Markers Reliable on Targeted Therapy?
- Complete Response, Partial Response, Stable Disease: What Each Means
- Do I Need Regular Brain MRIs on Targeted Therapy?
- How Doctors Measure Whether Targeted Therapy Is Working
- How Often Will I Need Scans on Targeted Therapy?
- How to Read a CT or PET Scan Report Without Panicking
- Is 'Stable Disease' Good News or Bad News?
- Scanxiety: How to Get Through the Wait for Scan Results
- Tumour Flare and Pseudoprogression: When Growth Isn't Really Growth
- Understanding PFS, OS and Median Survival Without Losing Hope
- What Happens at a Follow-Up Visit: A Walk-Through
- Which Blood Tests Are Repeated Every Month and Why
- ctDNA Monitoring: Can a Blood Test Predict Progression Early?
Long-Term Response, Stopping & Survivorship
- Am I Still a Cancer Patient? Identity After Long-Term Response
- Bone Health, Heart Health and Late Effects to Monitor
- Can You Ever Stop Targeted Therapy If the Cancer Is Gone?
- Drug Holidays: Are Planned Breaks Safe?
- Follow-Up Schedule After Stopping Targeted Therapy
- How Long Do You Have to Stay on Targeted Therapy?
- Long-Term Effects of Taking a TKI for 5 or 10 Years
- Restarting Treatment After a Break
- Treatment-Free Remission in CML: Who Can Stop Their TKI?
- Your Survivorship Care Plan: What Should Be In It
Resistance, Progression & Next Lines
- Being Told 'There Are No More Options': Is That Really True?
- Brain Metastases on Targeted Therapy: Does Your Drug Reach the Brain?
- Can You Continue the Same Drug After Progression?
- Combination Therapy to Overcome Resistance
- Do You Need Another Biopsy When the Cancer Progresses?
- Histologic Transformation: When Lung Cancer Changes Type
- How to Emotionally Process a Progression Scan
- Leptomeningeal Disease: Symptoms, Diagnosis and Treatment
- Life After ALK Inhibitor Resistance: Sequencing Your Options
- MET Amplification and Other Bypass Resistance Mechanisms
- Oligoprogression: When Only One or Two Spots Grow
- Primary vs Acquired Resistance: Two Very Different Problems
- Should You Change Hospitals After Progression?
- What Happens After Osimertinib Stops Working?
- What Is Sequencing and Why the Order of Drugs Matters
- Why Does Targeted Therapy Stop Working? The Biology of Resistance
Next step
Still not sure what applies to you?
Send your reports across and a senior medical oncologist will go through what they mean, what is known, and what the options actually are.
Common questions
Frequently asked questions
Is ctDNA the same as a tumour marker like CEA or CA 125?
No — they measure different things. A tumour marker like CEA or CA 125 detects proteins that the tumour produces; ctDNA detects actual DNA fragments shed by cancer cells into the blood. Both have a role in monitoring, and your oncologist may order both at different points in your care. Neither test is used in isolation — the result is always read alongside your clinical picture and imaging.
My ctDNA came back detectable after treatment finished. Does that mean the cancer has come back?
A detectable result after treatment — sometimes called molecular residual disease — does not automatically confirm a recurrence you can see on a scan. It is a signal that some cancer DNA is still circulating, which your team will monitor closely. What happens next depends on your cancer type, the level detected, and whether it is rising or stable. ASCO guidance in several cancer types recommends imaging to confirm before any treatment decision is made on a ctDNA result alone.
Why does my doctor still want a scan if my ctDNA is undetectable?
An undetectable ctDNA result is reassuring, but some tumours shed very little DNA even when active — meaning the test can miss disease that a scan would show. Imaging also gives structural information, such as the exact location and size of a tumour, that a blood test cannot. The two tests complement each other, and most oncology guidelines recommend imaging alongside ctDNA monitoring rather than instead of it.
How often will I need a ctDNA test?
The frequency depends on your cancer type, your stage, and the protocol your oncologist is following. It is generally not done at every visit. In active monitoring plans it may be ordered every few months, sometimes alongside your scan schedule. In post-treatment surveillance it may help space out imaging. Ask your oncologist how often it is planned for you and what each result is expected to tell them.
Is ctDNA testing available in India?
Yes, ctDNA testing is available through specialist molecular pathology laboratories in India, though it is not yet routine at every hospital. Samples may need to be sent to a reference laboratory, which adds a few days to the turnaround time. If your oncologist has ordered it, ask where the sample is being processed and when results are expected, so you are not waiting without a clear timeline.
My ctDNA has risen slightly since the last test. Should I be worried?
Not necessarily, but it is worth raising at your next appointment rather than waiting. A small rise needs to be read in the context of your own baseline, the overall trend across multiple tests, and the sensitivity of the assay used. Some variation between samples is expected. Your oncologist will look at whether the change is consistent, whether it is accompanied by symptoms, and whether it warrants bringing your scan forward. One slightly raised result rarely prompts an immediate change in treatment on its own.