When Breast Cancer Metastasizes to the Brain

Sometimes cancer doesn’t stay in its original place.

Metastatic cancer means the cancer has left its primary site and spread—that could be to the liver, brain, bones, or lungs. In the case of brain-metastatic breast cancer, it is the breast that is the primary site where the cancer started in the body.

What causes brain-metastatic breast cancer?

“If we knew the cause, we’d be that much closer to preventing it,” said Robert Rice, M.D., Ph.D., medical oncology physician at WellSpan Medical Oncology & Hematology – Adams Cancer Center in Gettysburg.

“We could have two women of the same age, with the same type of cancer, and one would have metastatic disease and another not,” Rice continued. “We’re still learning why this occurs, which is why continued support for cancer research is so important.”

Metastatic breast cancer is classified as stage IV breast cancer.

“All stage IV cancers are metastatic by definition,” he said.

The cancer metastasizes through one or more of the following processes:

• Cancer cells can access the lymph system and are often carried by the lymph system and the bloodstream to other parts of the body.
•Cancer cells can leave their primary site and seed other sites.

What are the symptoms of brain-metastatic breast cancer?
• Persistent, progressively worsening headaches
• Vision changes
• Seizures
• Vomiting or nausea, especially in the morning
• Behavioral changes

Depending on the location of the metastasis, patients may have other neurological deficits, such as aphasia (difficulty in speaking) and weakness, said Sherif Yacoub, M.D., radiation oncologist at the Adams Cancer Center.

This metastasis occurs mostly in the late stage of breast cancer, in about 10-15 percent of cases, Yacoub noted. This contrasts with other forms of cancer, such as small-cell lung cancer, where about 50 percent of malignancies metastasize to the brain.

How is brain-metastatic breast cancer diagnosed?
It is diagnosed through the presence of symptoms, but also on MRIs with contrast of the brain. It is not visible on a PET scan. If the patient has a history of cancer with two alarming symptoms, such as headaches and unexplained nausea, the physician may also do a CT scan of the brain to rule out brain metastasis.

“We’ve gotten better at reducing risk, with better treatment, preventive treatment, and improved identification of patients at risk,” said Rice.

How do you treat brain-metastatic breast cancer?
Steroids can be given for the edema caused by cancer in the brain and kept up during radiation. If there is only one single lesion, the physician could consider surgery or radiation. Surgery is, of course, invasive, and if there are several sites of cancer in the brain, surgery is not the best option.

Instead, the physician would give whole-brain radiation, according to Yacoub.

“We would treat with radiation,” said Rice. “There is some clinical evidence that immunotherapy can cross the blood-brain barrier to treat cancer that has spread to the brain. Most chemotherapy at the doses usually given cannot cross that barrier.”

The blood-brain barrier is an important mechanism for protecting the brain from fluctuations in plasma composition and from circulating agents, such as neurotransmitters and xenobiotics, capable of disturbing neural function.

But because of the blood-brain barrier, when a patient undergoes chemotherapy for metastasis, it doesn’t get concentrated in the brain. That’s why chemotherapy is not effective in brain metastasis.

If there are multiple brain lesions, the physician would give whole-brain radiation. You can’t repeat radiation on the same spot again, Yacoub said.

Brain-metastatic breast cancer is a treatable disease, as opposed to a curable one, said Yacoub. In the very early stages, the cure rate for breast cancer is 90 percent.

A “treatable” disease means the patient has to take medication or undergo treatment all one’s life, such as hypertension or hyperglycemia.

Another form of treatment is SRS, or stereotactic radiation, which is a very effective way of treating one to three lesions.

“In SRS, the doctor administers a high single dose of radiation,” said Yacoub.

But overall, the treatment of stage IV breast cancer is to add time and palliate symptoms; it is not curative. Again, Rice emphasized, that is why continued support for cancer research is so important. BW