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

An hour in a scanner. No radiation. 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 imaging is not on that list. No form of full-body scan appears among the tests NCI records as 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, described as the diagnosis and treatment of cancers that would not have caused problems

A whole-body scan is unusually good at causing the second and third. Scan every organ in a healthy person and you will find things. Bodies are lumpy and uneven. Most of what shows up is harmless. But once it is written 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 takes over a year of their life, for something that would never have caused trouble.

A normal scan has its own trap. It cannot rule out the cancers that standard screening is built to catch. So it is a poor reason to skip a mammogram or a bowel screening kit.

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 do need broader imaging. That includes people with a specific inherited condition, a strong family history, or a past cancer. But that is a medical decision made for a reason. It is not a service bought from an advert. 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 chase every line of the report yourself. Radiology language is descriptive and cautious on purpose. Phrases that sound alarming often describe completely ordinary anatomy.

Also check that a normal result has not quietly pushed something aside. Maybe you were due a bowel screening kit 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.