Breast cancer brain metastases occur when cancer cells from a primary breast tumor travel to the brain and form new tumors. This indicates the disease has spread beyond its initial site, representing a progression of the existing breast cancer.
Understanding Breast Cancer Brain Metastases
Breast cancer cells detach from the primary tumor and enter the bloodstream or lymphatic system. These circulating tumor cells then reach the brain. Once there, they must overcome the blood-brain barrier, a protective lining of small blood vessels that typically prevents harmful substances from entering the brain.
Certain proteins on the surface of these tumor cells may help them breach this barrier and establish themselves in brain tissue. Other proteins inside the cells may shield them from the brain’s immune response, allowing them to grow. This process involves specific molecular signatures that direct the cancer’s spread to the brain.
The incidence of breast cancer brain metastases has been increasing, as advancements in treatment allow patients with metastatic breast cancer to live longer. Brain metastases occur in about 10-15% of all women diagnosed with metastatic breast cancer, but the risk varies significantly depending on the breast cancer subtype.
HER2-positive and triple-negative breast cancers (TNBC) are more prone to developing brain metastases compared to hormone receptor-positive, HER2-negative subtypes. Approximately 25-50% of people with TNBC and 30-50% of those with HER2-positive disease may develop brain metastases. In contrast, the rate for hormone receptor-positive (HR+) disease is around 14%.
Identifying Symptoms and Diagnosis
When breast cancer spreads to the brain, it can cause various neurological symptoms. Common indicators include severe or persistent headaches, new or worsening seizures, and visual disturbances like blurred or double vision.
Individuals may also experience cognitive changes, including confusion, memory issues, or difficulty concentrating. Physical symptoms can involve impaired balance or coordination, and weakness or numbness, often affecting one side of the body. These symptoms arise from the pressure the growing tumors exert on brain tissue or from disruption of normal brain function.
Diagnosis begins with a clinical evaluation based on reported neurological symptoms. If brain involvement is suspected, advanced imaging techniques are utilized. Magnetic Resonance Imaging (MRI) is the preferred and most sensitive tool for detecting brain metastases, offering detailed views of tumor location, size, and number, often enhanced with contrast dye.
Computed Tomography (CT) scans may be used if an MRI is not feasible. If imaging results are inconclusive or if leptomeningeal disease (cancer spread to the membranes surrounding the brain and spinal cord) is suspected, a lumbar puncture may be performed to examine cerebrospinal fluid for cancer cells. A biopsy may also be conducted if the diagnosis remains uncertain.
Treatment Options for Brain Metastases
Treatment for breast cancer brain metastases involves a combination of local and systemic therapies. Local treatments directly address tumors in the brain. Surgery, or resection, involves the removal of one or more tumors, particularly when accessible and causing significant symptoms.
Radiation therapy is another local approach. Whole-brain radiation therapy (WBRT) delivers radiation to the entire brain, aiming to control widespread microscopic disease. Stereotactic radiosurgery (SRS) is a more focused radiation that delivers high doses to specific tumor sites with precision, minimizing damage to surrounding healthy brain tissue. Combining SRS with WBRT can improve intracranial tumor control rates.
Systemic treatments target cancer cells throughout the body. Chemotherapy uses powerful drugs to kill rapidly dividing cancer cells. Targeted therapies, such as HER2 inhibitors, block specific pathways cancer cells use to grow and spread, especially for HER2-positive breast cancer. For example, tucatinib, in combination with capecitabine and trastuzumab, has shown improved progression-free survival for patients with HER2-positive breast cancer brain metastases.
Immunotherapy helps the body’s immune system recognize and destroy cancer cells. Steroids are often prescribed to reduce brain swelling and pressure, alleviating symptoms. Treatment choice depends on the number and size of metastases, the specific breast cancer subtype, and the patient’s overall health.
Managing Life with Brain Metastases
Living with breast cancer brain metastases requires supportive care and maintaining quality of life. While the prognosis has historically been challenging, advancements in treatment have led to improved outcomes. Overall survival for breast cancer patients with brain metastasis is now closer to over two years, with a life expectancy of three years for those with HER2-positive tumors.
Symptom management is a significant aspect of care. Medications may be prescribed to control specific symptoms, such as anti-seizure drugs or corticosteroids to reduce brain swelling. Physical therapy, occupational therapy, and speech therapy can also help manage neurological deficits and improve daily functioning.
A multidisciplinary team approach is employed, involving oncologists, neurosurgeons, radiation oncologists, neurologists, and palliative care specialists. This collaborative effort addresses all aspects of the patient’s physical and emotional well-being. The focus remains on controlling cancer progression, managing symptoms, and supporting the patient in maintaining independence and comfort.