When cancer spreads from its original site to the brain, it’s known as brain metastasis. While a significant percentage of all patients with cancer develop brain metastases, the most common cancers to spread to the brain are lung, breast, melanoma, colon, and kidney tumors. Every year, an estimated 100,000-400,000 people in the United States are diagnosed with brain metastases, which are many times more common than cancer that initially forms in the brain.
It isn’t known for certain why some cancer types are more likely than others to spread to the brain, but a key factor appears to be attractive molecules called chemokines that draw tumor cells to the metastatic site. Adherent molecules in brain tissue may also be especially “sticky” to specific kinds of cancer cells.
About 85 percent of metastatic brain cancers are located in the cerebrum (the topmost portion and largest part of the brain), and 15 percent are located in the cerebellum (the bottom, back part of the brain), according to the American Brain Tumor Association. Metastasis to the brain and other parts of the central nervous system (CNS) is rare in children, accounting for about 6 percent of brain tumors in children.
Fortunately, the treatment of brain metastases has advanced substantially in recent years. Such treatments, which include surgery, radiation therapy, chemotherapy, immunotherapy, and targeted therapies, are helping patients live longer and maintain a good quality of life. At Dana-Farber and elsewhere, clinical trials are underway testing a variety of new therapeutic approaches.
For patients undergoing surgery, a variety of techniques help doctors remove as much tumor tissue as possible, while preserving healthy surrounding tissue. These include Functional MRI, a non-invasive imaging technique which helps doctors identify where important functions lie in the brain; Intra-operative MRI, which allows surgeons to see live, interior images of the brain while operating; and 3-D Navigation, which allows neurosurgeons to precisely locate deep-seated or small brain tumors.
Among the techniques for delivering radiation therapy to the brain are stereotactic radiosurgery, which delivers a very high dose of radiation to a specific region of the brain, and stereotactic radiotherapy, which is often used to deliver multiple, smaller doses of radiation to large tumors. At Dana-Farber and Brigham and Women’s Hospital, radiation oncologists and physicists have developed a technique to treat many targets in the brain in one session, an approach called one-isocenter, multi-target volumetric modulated arc therapy.
Advances in chemotherapy, targeted therapies, and immunotherapy have made it possible to use the same treatment to treat metastatic disease in the body and metastatic tumors in the brain in some patients.
Learn more about how we treat brain metastases.