Multi-cancer blood test or whole-body MRI, which suits you?

Written By Sama Samy

A multi-cancer blood test looks for cancer signals in the blood, while a whole-body MRI looks for structural changes in organs. The blood test suits adults over 50 who want to add to routine screening. MRI suits people with specific inherited risks. Neither replaces established screening. The Online GP by The Wellness helps you choose after a doctor-led assessment.

Key points

  • The Galleri trial in England, the first randomised trial of a multi-cancer blood test, included more than 140,000 people aged 50 to 77, with results published in September 2026.

  • About half of trial participants with a positive blood test were diagnosed with cancer, and fewer stage IV cancers were seen in people offered the test.

  • The trial did not meet its main goal of a statistically significant reduction in stage III and IV cancers combined.

  • Whole-body MRI detects cancer in around 1% to 2% of people without symptoms, with incidental findings in up to 97% of scans, according to a 2026 radiology review.

  • The Royal College of Radiologists does not advise whole-body scans without a clear medical indication.

What does a multi-cancer blood test do?

A multi-cancer early detection blood test looks for fragments of tumour DNA circulating in the blood. A positive result suggests a cancer signal and predicts where in the body it may come from, which guides further tests. The best-studied test screens for more than 50 cancer types, including several with no routine screening.
The Galleri trial results from England, published in September 2026, showed the test detected far more early-stage cancers than routine screening alone. About 50% of participants with a positive test had cancer diagnosed.
Our existing guide to what the Galleri trial in England actually found covers the trial in depth.

What did the Galleri trial not show?

The Galleri trial in England did not show a statistically significant reduction in the combined number of stage III and IV cancers, which was its main goal. It did show fewer stage IV cancers among people offered the test, and longer follow-up is needed to know the effect on survival.
The researchers at Queen Mary University of London describe the test as a genuine addition to screening that cannot replace it. A negative result does not rule out cancer, and the test misses many early cancers.
"A multi-cancer test is a useful extra layer for the right person, not a guarantee," says Dr Adel Elalfy, Head of Primary Care at The Online GP by The Wellness. "I always pair it with the screening people are already entitled to, and a clear plan for what happens if it is positive."
Ask a doctor on WhatsApp whether a multi-cancer blood test suits you.

What does a whole-body MRI do?

A whole-body MRI takes detailed images of the organs from head to thighs without radiation. It shows structural changes, such as tumours in solid organs, aneurysms and liver disease. It is less effective for early bowel cancer, skin cancer and small lung changes, and it does not measure anything in the blood.
A 2026 radiology review reports cancer detection in around 1% to 2% of people without symptoms on screening whole-body MRI, with incidental findings in up to 97% of scans. Our guide to whether a whole-body MRI is worth it explains the evidence.

Which test suits which person?

The right test depends on age, family history, inherited risk and what you want to know. A doctor-led assessment matches the test to your risk, and for many people the best first step is making sure routine screening and a good blood panel are up to date.

  • Adults over 50 wanting to add to routine screening may consider a multi-cancer blood test.

  • People with inherited cancer syndromes, such as Li-Fraumeni syndrome, are advised to have annual whole-body MRI.

  • People with a strong family history of a specific cancer usually benefit most from targeted screening for that cancer.

  • People with symptoms need a diagnostic assessment, not a screening test.

Our guide to what a full private blood test should include covers the foundation most people should start with.

Can I have both tests?

Some people choose both a multi-cancer blood test and a whole-body MRI, because they look for cancer in different ways. Having both increases the chance of finding something, including harmless findings that need follow-up. A doctor should agree the plan, and the follow-up pathway, before either test.
The doctor also checks that routine screening, such as bowel, breast and cervical screening, is up to date. These programmes have the strongest evidence and should never be replaced by a private test.
Plan your screening with a doctor on WhatsApp.

How much do these tests cost?

Full-body MRI in the UK typically costs £1,500 to more than £3,500 in 2026, according to a WeCovr guide updated August 2026. At The Online GP by The Wellness, the Executive Physical starts from £2,995 and blood panels from £350.
Multi-cancer blood tests and MRI scans are quoted per patient from the clinic's partner list, and the team confirms fees on WhatsApp before booking. The doctor's assessment starts with a classic GP appointment from £150. Ask about screening fees on WhatsApp.

Can a doctor tell me which test I need?

Yes. The Online GP by The Wellness offers a free suitability review. Send your age, family history, previous screening and any symptoms on WhatsApp. A doctor either recommends a specific test or tells you plainly that routine screening is the right plan for now.
Start your free suitability review on WhatsApp.

Frequently asked questions

Does a negative multi-cancer blood test mean I do not have cancer?

No. A negative result lowers the likelihood of some cancers but does not rule cancer out. Continue routine screening and report any new symptoms.

What happens if a multi-cancer blood test is positive?

The result predicts where the signal may come from, and the doctor arranges scans and specialist tests to find or rule out cancer. About half of positive results in the Galleri trial in England led to a cancer diagnosis.

Is a whole-body MRI safe?

MRI uses no radiation and is very safe for most people. The main risk is incidental findings that lead to further tests. A safety questionnaire checks for implants and metal.

Should I replace bowel or breast screening with these tests?

No. Established screening programmes have the strongest evidence and should continue alongside any private test.

Sources

  • Queen Mary University of London, results of the Galleri randomised trial in England, September 2026

  • Radiology Advances, How to implement a radiologist led whole-body MRI screening programme, 2026

  • Medscape News UK, When full-body scans trigger a medical cascade, 2026

  • WeCovr, Full body MRI scan cost UK 2026, August 2026
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Sama Samy
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