Brain Metastases
Brain metastases are secondary tumors that occur when cancer cells spread from their original site (primary cancer) to the brain through the bloodstream. These are the most common type of brain tumor in adults, affecting 10-30% of cancer patients, and represent a significant complication that requires specialized treatment to manage symptoms and extend survival.
What is it?
Brain metastases occur when cancer cells break away from a primary tumor elsewhere in the body, travel through the bloodstream, and establish new tumors in the brain. These secondary brain tumors are more common than primary brain tumors, accounting for approximately half of all brain tumors diagnosed. The process of metastasis involves complex biological mechanisms where cancer cells must survive in the circulation, cross the blood-brain barrier, and successfully colonize brain tissue. Brain metastases can be single or multiple, and their characteristics often reflect the primary cancer type.
Approximately 200,000-300,000 people in the United States are diagnosed with brain metastases annually. The most common primary cancers that metastasize to the brain are lung cancer (40-50% of cases), breast cancer (15-25%), melanoma (5-20%), kidney cancer (5-10%), and colorectal cancer (5-10%). Melanoma and lung cancer have the highest propensity to spread to the brain. Brain metastases typically appear in the cerebral hemispheres at the junction of gray and white matter, where blood flow slows and vessels narrow, creating favorable conditions for cancer cells to lodge. About 80% of brain metastases occur in the cerebral hemispheres, 15% in the cerebellum, and 5% in the brainstem.
Important to Know
Brain metastases significantly impact quality of life and prognosis, but treatment advances have improved outcomes. Symptoms depend on the location, size, and number of metastases and may include headaches (often worse in the morning), seizures (particularly with new-onset seizures in adults with known cancer), progressive neurological deficits (weakness, numbness, vision or speech problems), cognitive changes, balance difficulties, or personality changes. Treatment is multidisciplinary and individualized based on the number and size of metastases, primary cancer type, overall cancer burden, and patient performance status. Options include surgical resection for single or limited metastases, stereotactic radiosurgery (highly focused radiation, particularly for 1-4 lesions), whole brain radiation therapy, targeted therapy or immunotherapy for specific cancer types, and supportive care including steroids to reduce swelling. Recent advances in targeted therapies and immunotherapy have significantly extended survival for some patients, particularly those with lung cancer, melanoma, and breast cancer with specific molecular characteristics.