• Brain metastases: Cancer has spread to the brain from another part of the body.
• Leptomeningeal disease: Cancer has spread to the leptomeninges, the tissue that lines the spinal cord, from another part of the body.
• Choroid metastases: Cancer has spread to parts of the eye from another part of the body.
• Pleural effusion: An accumulation of fluid in the pleural cavity, the space between the lungs and the interior walls of the chest. Pleural effusion may result when breast cancer spreads to the lungs or the pleural cavity.
• Pericardial effusion: An accumulation of fluid in the sac surrounding the heart. Pericardial effusion may result from the direct spread of cancer from adjacent organs like the lungs, or from other parts of the body.
• Biliary obstruction: Blockage of the bile ducts that may result from metastatic tumors, benign tumors, or cysts.
• Ureteral obstruction: Blockage of the tubes going from the kidneys to the bladder.
• Impending pathologic fracture: Cancer has invaded and weakened the bone and the patient is at risk for a fracture.
• Pathologic fracture: A fracture through a bone that has been affected by a tumor. Pathologic fractures can spread tumor cells through the hematoma and increase the risk of local recurrence.
• Cord compression: Compression of the vertebrae (backbone) that often results from a cancer in the chest region.
• Painful lesions: Localized and abnormal changes in the structure of an organ or tissue resulting from disease or injury that causes great discomfort. Lesions may be benign or malignant.
• Plexopathy/radiculopathy: Injury to the plexus (interlacing nerves or blood vessels), or to the nerve roots.
• Superior vena cava syndrome (SVCS): The obstruction of the blood flow in the superior vena cava, the major vein that empties blood into the heart. SVCS occurs when the vein is compressed. The disorder may be a life-threatening complication of some cancers and other disorders. Symptoms include painful breathing or shortness of breath, a feeling of fullness in the head, and facial swelling. Prognosis of SVCS depends on the prognosis of the underlying disease.
• Extensive locoregional disease: Cancer that has spread to many regions of the body.

Since metastatic breast cancer is generally not considered curable, a balance must be found between the side effects of treatment and how well a patient is responding to that treatment. Ideally, improvement of symptoms will outweigh te side effects of therapy. A patient's overall response to therapy is monitored by examining areas where the tumor may be felt (such as lymph nodes) or by usin CT scans or bone scans. A general evaluation of side effects as well as certain blood tests are considered when determining the patient's overall response and any necessary changes in therapy.

For patients whose tumors are hormone receptor-positive, hormonal therapy is first tried. Patients who have already been on tamoxifen recently or whose tumors progress while on tamoxifen can be given a trial of “second line” hormonal therapies such as oophorectomy (either surgical or with medications, for premenopausal women), aromatase inhibitors (for postmenopausal women), or megesterol acetate. These drugs are usually fairly well tolerated and are continued as long as the overall cancer is felt to be responding or not progressing.