MRI Can Reveal If Breast Cancer Has Spread to the Brain
Breast cancer that spreads from the breast to the brain — known as a brain metastasis — can cause symptoms ranging from a bad headache and dizziness to memory problems and seizures. When breast cancer spreads it’s called metastatic breast cancer or stage IV cancer.
If doctors think you might have brain metastasis, they will do a stat order for a brain MRI, usually within 48 hours, says Kelly Orwat, MD, a radiation oncologist and associate director at Mercy Medical Center in Baltimore.
What to expect with a brain MRI
A brain MRI is a type of scan that uses a strong magnet and radio waves (which are different from radiation) to create a detailed picture of the brain.
MRIs may or may not use contrast, where doctors inject dye through an IV into your vein. This helps tumors stand out on the images. But when doctors look for brain metastases, they will always use contrast.
During an MRI, you’ll lie on a table in a gown, and the technologist will place a device on your head that looks like a helmet, known as a head coil. This head coil helps images look clearer and more detailed on the scan. The contrast dye is injected into your vein, which might feel cold going in. This contrast dye doesn’t contain iodine (which is used for other types of scans), so if you have an iodine allergy you don’t have to worry.
You’ll get earplugs or headphones for comfort, since the machine can make a lot of loud noises. It can be helpful to close your eyes or request an eye mask before the table slides into the MRI machine, especially if you’re claustrophobic. But you’ll also get a call button to hold onto if you need a break or feel uncomfortable.
For a brain MRI, only your head and shoulders go into the tunnel, and the rest of your body remains outside the machine. The scan usually takes about an hour when contrast dye is used.1
When are brain MRIs ordered?
A brain MRI is ordered when you’re having brain-related symptoms, according to Orwat. These symptoms can include:
headaches that are outside of what’s normal for you, are persistent, or don’t go away with pain medication
vision changes (double vision, blurred vision, loss of visual field, or seeing strange shapes in your vision)
weakness or numbness in your body (such as a hand or a leg feeling weak)
slurred speech
mood changes
seizures
severe nausea that doesn’t respond to treatment
Let your oncologist know if you have any of these symptoms, or if anything feels out of the ordinary.
Brain MRIs are covered by insurance when they’re considered medically indicated, meaning there’s a valid reason (such as having brain-related symptoms) for the test.
What does a brain MRI show?
Doctors are looking for a tumor, or what doctors call an enhancing lesion, in the brain. This means the spot “lights up” from contrast dye, which is why a brain MRI always needs to be done using contrast.
A normal brain MRI means there are no signs of metastases, both halves of the brain look the same, and there's no fluid leaking or swelling, Orwat explains.
While a PET (positron emission tomography) scan is also used to see if cancer has spread, Orwat says a PET scan can’t find brain metastases. PET scans work by lighting up active areas. Since the brain is always highly active, it stays lit up for a PET scan, and tumors wouldn't be spotted.
Sometimes, Orwat says, it may not be brain metastases causing your symptoms. Instead, these symptoms may be caused by cancer spreading to another body area:
Tumors in soft tissues around the face could affect nearby nerves, causing facial numbness.
Spine tumors can cause numbness and weakness in parts of the body.
Tumors in the eye socket may cause double vision.
Tumor cells in the fluid around the brain may lead to headaches, vision problems, hearing loss, and numbness.
Brain MRIs can still detect issues in these areas, since they take a scan of your whole head. “So even if the brain is negative [for cancer], there might be something else going on,” explains Orwat. “Your doctor is going to know to do further testing from there.”
If a brain MRI identifies a problem
Brain metastases are typically treated, Orwat says, though you and your oncologist will make this decision together. So even if you’re currently getting radiation treatment for breast cancer, your oncologist will treat the metastases at the same time, Orwat adds.
The type of treatment you have for brain metastases depends on their size and how many there are. When doctors find brain metastases in people with metastatic breast cancer, there are typically between one and three, according to Orwat. In this case, doctors usually do stereotactic radiosurgery,2 which sends focused radiation straight to each of the tumors in a single treatment.
A neurosurgeon may remove a single large tumor that’s causing a lot of symptoms. If there are multiple tumors, or your doctor doesn’t want to remove a single tumor for safety reasons, then you’ll likely have radiation treatments, Orwat says.
Do people with metastatic breast cancer get routine brain MRIs?
Brain MRIs aren’t usually ordered for people with metastatic breast cancer if they’re not having any symptoms. A 2025 study in the journal Neuro-Oncology found that about 14% of people with metastatic breast cancer had brain mets without any symptoms.3
While that sounds scary, Orwat says this is uncommon, and it’s not something she wants people to worry about. “It comes down to what the risk is of finding something,” she says.
The current guidelines don't recommend MRIs for people without symptoms,4 but researchers continue to study whether people with metastatic breast cancer would benefit from them on a routine basis.
People with small cell lung cancer routinely get brain MRIs because of the high risk of cancer spreading to the brain. Breast cancer doesn't behave like that, says Orwat, and instead tends to travel to the lymph nodes, lungs, and bones, which is why doctors look for spread in those places first.
Keep your oncologist informed of any symptoms
Symptoms of cancer spreading to the brain can appear as early as during radiation treatment or as late as 10 to 15 years after treatment ends, according to Orwat. Regardless of how long it's been since your treatment, tell your care team about any symptoms you're having.
“Never feel like you're being pushy or asking too many questions. You're your own first line of defense, and you're never wrong to advocate for yourself,” says Orwat.
If you don't feel like you're getting what you need from the first doctor, talk to another doctor on your team. “You usually have three doctors on your team: a medical oncologist, a radiation oncologist, and your breast surgeon. So talk to all three of them if you need to,” says Orwat.
Your oncologist might say a certain side effect is common for a specific treatment. If the symptom can be explained, and you both feel good about it, then it can put your mind at ease. But if something doesn't seem right — whether to you or your doctor — your doctor will likely order a scan, Orwat says.
“Peace of mind is worth something,” explains Orwat. “Even if the degree of suspicion isn't terribly high, it might still be high enough — paired with your worry — that it's worth getting the scan. We don't want to miss something.”
References
1. UC Davis Health. “How long is my MRI exam?” Available at: https://health.ucdavis.edu/radiology/mymri/mymri-faq.html
2. Peña-Pino I, Chen CC. Stereotactic Radiosurgery as Treatment for Brain Metastases: An Update. Asian J Neurosurg. 2023; 18(2):246-257.
3. Ahmed KA, Kim Y, et al. Phase II trial of brain MRI surveillance in stage IV breast cancer. Neuro-Oncology. 2025; 27(6):1550-1558.
4. Sammons S, Lamba N, Lin NU. Brain imaging screening in metastatic breast cancer: Is it time to rethink clinical guidelines and practice? Breast. 2025; 84:104616.