Browse evidence-based analysis of health-related claims and assertions
When doctors stop screening for breast cancer, they can't tell exactly how many of the tumors found would never have caused harm, even with fancy math, because the data they have just isn't detailed enough to give clear answers.
Quantitative
When doctors scan lungs with a special X-ray to find cancer early, they sometimes find cancers that would never have caused harm. But if they watch people for a longer time, fewer of these harmless cancers show up—suggesting that the early scans just found cancers sooner, not that they found more dangerous ones.
Causal
When doctors use a special low-dose CT scan to find lung cancer early, about 1 in 5 of the cancers they find might never cause harm — meaning the person would never have known about them if not for the scan, and they wouldn’t need treatment.
If you screen 320 people who are at high risk for lung cancer with a special scan, you might save one life—but you’ll also find and treat about 1.4 cancers that would never have hurt them. So for every 100 lives saved, around 138 people get treated for cancers that didn’t need treatment.
When lung cancer is found through a special low-dose CT scan, almost 8 out of 10 of a certain type of tumor might be harmless and would never hurt the person if left alone—only the scan found it, and it wouldn’t have caused any problems otherwise.
When doctors use a low-dose CT scan to check high-risk people for lung cancer, about 1 in 5 of the cancers they find might never have caused any problems — meaning those people could be treated for something that didn’t need treating, leading to stress, side effects, and extra costs.
Doctors are testing if a full-body MRI scan can help healthy people stay healthy over time, without using radiation or cutting into the body.
Descriptive
A program called the Hercules Project is giving free whole-body MRI scans to people who can’t usually afford them, to see if cancer is found more often in poorer communities.
Doctors are testing if a full-body MRI scan can find hidden cancers sooner in people who feel fine, so they can start treatment faster.
Doctors are testing whether full-body MRI scans can reliably spot cancer by checking how often they correctly find it (and don’t miss it), using agreed-upon rules to interpret the images.
Using a full-body MRI scan on people who feel fine might help doctors find hidden cancers or other serious health problems early, especially when they use special rules to decide what needs follow-up.
Correlational
When doctors use two different scans to check for bone damage in multiple myeloma, they usually get the same results—but about 1 in 10 times, the MRI sees something the PET/CT scan misses.
For some people with an early form of blood cancer called smoldering myeloma, a special full-body scan (MRI) can spot hidden cancer cells in the bone marrow—even when there are no visible tumors—and this might help doctors decide to start treatment sooner.
A full-body MRI scan can find serious hidden health problems—like possible cancer or spinal issues—in people with certain types of blood cancer, even when a different scan called FDG-PET/CT misses them.
When doctors use both a full-body MRI and a special PET/CT scan together to check for multiple myeloma, they’re more likely to change the patient’s treatment plan than if they only use one scan alone.
A full-body MRI scan is better at spotting early signs of bone marrow cancer in certain types of myeloma than the PET/CT scan, especially when the cancer looks spread out in tiny spots — and this might change how doctors decide to treat patients.
Using a full-body MRI scan on people who feel fine can sometimes find hidden health problems they didn’t know they had—and some of those problems might need a doctor’s attention.
Using a full-body MRI scan on people who feel fine can find hidden health problems that doctors might need to treat—before those people start feeling sick.
When doctors scan healthy people’s whole bodies with MRI and find unexpected issues, most of those findings turn out to be important enough to check further—only about 1 in 10 are harmless.
When people who feel perfectly fine get a full-body MRI scan, doctors often find unexpected things like bumps or changes in their spine, belly, muscles, or organs — and this happens a lot, even when they have no symptoms.
Using a full-body MRI scan might help find cancers in body parts where doctors don’t normally screen people, like without a regular test.
When doctors scan the whole body with an MRI on people who feel perfectly fine and have no symptoms, they find cancer in about 1 in 64 of them.
Getting a full-body MRI scan to check for problems isn't worth the cost because it often finds harmless things that cause stress and tests, and no one has proven it helps people live longer.
Sometimes, a full-body MRI scan might miss a serious problem, making doctors think everything’s fine when it’s not — and that delay could lead to really bad health results.