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Brain metastases from breast cancer.

AS We have long known that breast cancer can metastasize to the brain, and with recent improvements in systemic therapy that control metastases in sites such as the bone, liver, and lung, we now see patients living longer, which has allowed brain metastases that might have otherwise remained occult to manifest. We know from autopsy studies that brain metastases can be found in approximately 20–25% of women. Currently, approximately 10–15% of patients with a diagnosis of breast cancer may expect to have brain metastases, which certainly represents a clinical feature associated with a poor prognosis. Survival for patients with brain metastases is commonly measured in months and not years. We also recognize that there are specific molecular subtypes of breast cancer that seem to have a greater propensity for metastasis to the central nervous system, specifically the triple negative breast cancers—the estrogen-, progesterone-, and HER2 receptor–negative breast cancers—as well as breast cancers that overexpress HER2. In these subsets of cancer, brain metastasis can occur in approximately one-third of all patients.