Medical Oncologist
Biomarker & Molecular Testing
ctDNA and MRD Testing: — Tracking Cancer Through a Blood Test
A blood test can now detect fragments of cancer DNA circulating in your body — without a biopsy. Whether that test applies to you depends on your cancer type and what question your team is trying to answer.
Medically reviewed by Dr. T. Raghavender Reddy, Medical Oncologist, MBBS · DM (Medical Oncology) · MD (Radiation Oncology) · Last reviewed August 2026
- A blood draw, not a biopsy — ctDNA testing uses a standard blood sample to look for cancer DNA — no needle into a tumour.
- Tracks what scans can miss — It can detect tiny amounts of residual cancer in some situations earlier than imaging can resolve a lesion.
- Shows whether treatment is working — A falling ctDNA level during treatment can indicate the cancer is responding.
- Not for every cancer or every question — Shed levels vary by tumour type; your oncologist will tell you whether the test applies to your situation.
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ctDNA testing detects fragments of cancer DNA circulating in your bloodstream. It can reveal whether cancer is still present after treatment, track how the disease responds, or catch a recurrence earlier than a scan in some cancers. Whether it applies to your situation depends on your cancer type, stage, and what clinical question your team is trying to answer.
What is ctDNA testing and how does it work?
ctDNA stands for circulating tumour DNA — small fragments of cancer DNA shed by a tumour into the bloodstream. A ctDNA test collects a blood sample and searches those fragments for the specific mutations that identify your cancer. MRD testing — minimal residual disease — uses the same approach to ask a narrower question: is any cancer still detectable after treatment that aimed to eliminate it completely?
Results typically take two to three weeks from the day the sample reaches the laboratory, though some specialist panels take longer and rapid-turnaround options exist for specific mutations. Costs vary with the breadth of the panel and change often enough that asking your care coordinator for a written estimate before the test is ordered is worthwhile.
Unlike a tissue biopsy, a blood draw can be repeated easily, which makes ctDNA useful for monitoring over time rather than just for initial diagnosis. Its limitation is that shed levels vary — some cancer types release very little ctDNA even when disease is active, so a negative result does not always mean the cancer is gone. Your oncologist will weigh both what the test can tell you and what it cannot before recommending it.
Is a liquid biopsy as accurate as a tissue biopsy?
| ctDNA (liquid biopsy) | Tissue biopsy | |
|---|---|---|
| What is collected | A blood sample from a vein | Tissue taken from the tumour by needle or surgery |
| What it measures | Cancer DNA fragments and mutations circulating in the blood | Tumour cells, mutations, proteins, and tissue structure |
| Typical turnaround | Two to three weeks (varies by panel and laboratory) | Five to ten working days for standard histology |
| Can it be repeated? | Yes — a blood draw each time, no procedure needed | Requires a new biopsy procedure with procedural risk each time |
| Best used for | Monitoring treatment response, detecting residual disease, surveillance for recurrence | Initial diagnosis, before major treatment decisions, confirming an unclear ctDNA result |
| Main limitation | Some cancers shed very little DNA; a negative result does not confirm the cancer is gone | Not accessible for all tumour sites; one sample reflects one part of the tumour at one point in time |
| Indicative cost (India, 2026) | Varies by panel breadth — ask for a written estimate before ordering | Varies by site and complexity; ask your team or coordinator |
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
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When should you ask your oncologist about ctDNA testing?
- Your treatment has ended and you want to know whether residual cancer is detectable in your blood
- Your imaging results after treatment are unclear or difficult to interpret
- You have had surgery and your team is deciding whether chemotherapy is needed
- Your cancer has returned once before and you want closer monitoring between scans
- Your cancer type is one where ctDNA is an established monitoring tool — such as colorectal, lung, or breast cancer
- Your oncologist has mentioned it but you want to understand what a positive or negative result would mean for your care
What does your ctDNA result mean, and what happens next?
What does a positive ctDNA result mean after treatment?
A positive result after surgery or treatment means the test has found cancer DNA still circulating in your blood. This indicates residual disease — cancer cells that may not yet be visible on a scan. What happens next depends on your cancer type and stage: your oncologist may recommend additional treatment, a repeat test in a few weeks to check the trend, or closer surveillance with imaging. A single positive result is rarely acted on in isolation; the direction of change over multiple tests usually carries more weight than a single reading.
What does a negative ctDNA result mean?
A negative result means no cancer DNA was detected at the sensitivity level of the test used. In many cancers this is a reassuring finding, and NCCN and ESMO guidance notes that undetectable ctDNA after treatment is associated with better outcomes in several tumour types. However, it is not a guarantee. Some cancers shed very little DNA even when active, and every test has a sensitivity floor below which it cannot detect. Your oncologist will interpret a negative result alongside your scans and clinical assessment rather than as a standalone answer.
Can ctDNA testing replace my regular CT or PET scan?
Not currently. ctDNA and imaging give complementary, not identical, information. ctDNA can detect the presence of cancer DNA before a scan can resolve a visible lesion in some situations. Imaging can show where in the body the disease is, how large it is, and whether it is responding structurally. NCCN and ASCO guidance recommends using ctDNA alongside imaging rather than in place of it. If your team is recommending both, that is consistent with current standard practice.
I had ctDNA testing done elsewhere — can CION use that report?
Yes. If you already have a ctDNA report from another centre in India or from a laboratory abroad, bring the full report to your appointment at CION — not just the summary page. Your oncologist will review the panel used, the mutations identified, and the stated sensitivity before interpreting the result. If the panel used is not one your oncologist recognises, or the methodology is unclear, they may request additional testing rather than acting on the earlier report alone.
Does insurance cover ctDNA testing in India?
Coverage varies significantly between insurers and policy types, and it is changing as ctDNA enters more clinical guidelines. Some group health policies cover it when the test is ordered as part of a cancer treatment protocol; others classify it as investigational and exclude it. Before the test is ordered, ask your insurance coordinator specifically whether the test code your oncologist is using appears in your policy schedule. A pre-authorisation letter from your oncologist explaining the clinical indication can help. CION patient coordinators can assist with the documentation.
Is ctDNA testing the same as circulating tumour cell (CTC) testing?
No, though both are types of liquid biopsy. ctDNA is free-floating DNA shed by cancer cells into the blood. Circulating tumour cells are intact cancer cells that have broken away from the tumour and entered the bloodstream — a different thing entirely. The two tests detect different things and have different validated uses. Most oncology guidelines, including those from NCCN and ASCO, focus their ctDNA recommendations on specific molecular monitoring applications. Your oncologist will specify which type of liquid biopsy is relevant to your situation.
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Common questions
Frequently asked questions
Is ctDNA testing available in India?
Yes, and access is expanding. Several accredited laboratories now offer ctDNA panels, with turnaround from most major cities typically running two to four weeks for comprehensive panels. Some specialist tests require the sample to be sent to a reference laboratory, which may add time. Your oncologist will tell you which test is appropriate and whether the report will be ready in time to inform your next treatment decision. CION centres can coordinate the collection and referral.
Which cancers is ctDNA monitoring most established for?
ctDNA monitoring has the strongest evidence base in colorectal cancer, non-small cell lung cancer, and breast cancer, according to NCCN and ESMO guidelines. It is also used in bladder, ovarian, and several other solid tumour types. For blood cancers, similar monitoring is done through different assays. Whether ctDNA is a validated monitoring tool for your specific cancer type is worth putting directly to your oncologist, because the strength of evidence varies considerably by tumour type.
How often do I need ctDNA testing?
Frequency depends on the clinical question. If it is being used to monitor for recurrence after curative treatment, your oncologist might recommend testing every three to six months alongside imaging. If it is tracking treatment response, the timing aligns with your treatment cycle. NCCN and ASCO guidance leaves the interval to clinical judgement based on cancer type and the purpose of the test — there is no universal standard that applies to everyone.
Can a negative ctDNA result reassure me that my cancer is gone?
It is a positive sign but not a guarantee. A negative result means no cancer DNA was detected at the level of sensitivity that test can achieve. For several cancer types, undetectable ctDNA after treatment is associated with better long-term outcomes in data reviewed by ESMO and ASCO. Your oncologist will combine the result with your imaging and your clinical picture. No single test gives a definitive answer in either direction, and your oncologist will not base a major decision on one result alone.
What is MRD testing and is it different from ctDNA testing?
MRD stands for minimal residual disease. MRD testing uses ctDNA as its underlying method but asks a narrower question: is any cancer detectable at all after treatment that aimed to eliminate it completely? ctDNA testing is the broader category; MRD is a specific application of it focused on post-treatment surveillance. Both rely on the same blood draw and laboratory process. Whether your oncologist calls it ctDNA testing or MRD testing often reflects the context in which it is being used.
Does CION offer ctDNA or MRD testing?
Yes. Your oncologist at a CION centre can order ctDNA or MRD testing as part of your care. The blood sample is collected at the centre and sent to an accredited partner laboratory; results are reviewed with you at your next appointment or communicated earlier when they are needed for a treatment decision. Ask your oncologist at your next visit whether this test is relevant to your cancer type and where you are in your treatment.