Whole-body MRI scans as cancer screening: are they worth it?

This page is for anyone thinking about a whole-body MRI to check for cancer. It explains what the evidence shows and what to do if you have already had one.

A picture of your whole body. Peace of mind. Clinics that advertise this know exactly what they are selling.

The problem is the logic behind it. It does not match how screening really works.

NCI keeps a list of screening tests shown to reduce deaths from cancer. The list is short:

• Mammography for breast cancer, for women aged 40 to 74
• HPV tests and Pap tests for cervical cancer, from age 21 to 65
• Colonoscopy, sigmoidoscopy and stool tests for colorectal cancer, from age 45 to 75
• Low-dose CT for lung cancer, for people aged 50 to 80 with a heavy smoking history

Whole-body MRI is not on that list. NCI's page does not list any full-body scan among the tests shown to reduce cancer deaths.

There is a reason the list is short. To get on it, a test must be shown to cut deaths from that cancer. That is a high bar. Most ideas do not clear it.

NCI also names methods that have not been shown to cut cancer deaths. These include clinical breast exams, breast self-exams and skin exams. NCI records that expert groups generally advise against routine PSA testing for men at average risk.

That is worth sitting with. Some things feel obviously useful. They were studied, and they did not give the benefit people assumed. Gut instinct is a poor guide here.

NCI lists three kinds of screening harm:

• Bleeding or other physical damage
• False-positive or false-negative test results
• Overdiagnosis and overtreatment, meaning the diagnosis and treatment of cancers that would not have caused problems

A scan of the whole body can raise the chance of the second and third. Scan every organ in a healthy person and you may find things that need follow-up. Once a finding is in a report, someone usually has to chase it.

The question is never "can this test see something?" It is "does using it leave people better off?"

Say a scan shows a small spot in a kidney, or a nodule in a lung. You rarely get a clean answer. More often you get a sequence. A repeat scan in a few months. Then maybe another. Perhaps a biopsy. And a long stretch of not knowing.

Some people handle that fine. For others it is a long, stressful wait.

A normal scan is not a reason to skip a mammogram or a colorectal screening test. Those tests are the ones NCI lists as shown to reduce deaths.

Maybe you want this because you want to be proactive. The better move is simpler. Make sure you are up to date on the screening that has been proven to help. Learn which of it applies at your age.

Some people may need different or extra testing because of their history. That is a medical decision made for a reason. It is not a service bought from an ad. Bring the question to a clinician who knows your history. They can tell you whether you are one of those cases.

Plenty of people read about this after the scan, not before. Sometimes the scan came as a gift or a workplace perk. If that is you, regret is not useful. Handling the report well is.

Take it to a clinician who knows your history. Ask two questions. Which of these findings need any action? And which ones turn up routinely in healthy people?

Try not to interpret every line of the report on your own. Ask your clinician what each finding means.

Also check that a normal result has not quietly pushed something aside. Maybe you were due for a colorectal screening test or a mammogram. A clear whole-body scan does not replace either one. Those tests exist because they have been shown to reduce deaths.

Peace of mind is a reasonable thing to want. It is worth buying from the tests that have earned it.