About 35% of patients with breast cancer will develop metastases. 80% of these will be in the bone, 60-70% in the lung, 50% in the liver and 10-20% in the brain.
With metastases in the bone, osteoclasts (dismantle and remove damaged bone) become overactive which means more bone is broken down than replaced. Symptoms of this include pain near the affected area (this can worsen at night or at rest), hypercalaemia, fractures. Treatment for bone metastases can involve radiotherapy, surgery or biophosphate therapy which decreases the number of osteoclasts (and also their function), to allow new bone to be produced.
Frequently breast cancer metastasises first into the lung. This may present as shortness of breath, pain, or a dry cough. Other patients may be completely asymptomatic, and therefore a chest x-ray may be required to show the metastasis. A biopsy may be taken to ensure correct diagnosis.
Treatment is determined by the presence of other metastases, the patient’s health status and previous treatment history. Options include chemotherapy, hormone therapy and targeted therapy. Surgery is generally not an option because of the frequent distribution of the metastases, but may be considered if there are solitary tumours. Sometimes vena cava obstruction can occur due to lymph nodes or tumour putting pressure on the superior vena cava. This can cause stridor, faical swelling or dilation of major superior veins. This requires urgent assessment and treatment. Radiotherapy and steroids may be prescribed to reduce the obstruction caused by the swelling, occasionally a stent may be required. Pleural effusions are also a symptom of lung metastases, these need to be drained if large.
Liver metastases however, may present as bloating, nausea, ascites, abdominal pain, weight loss, back pain, jaundice or abnormal liver function tests. Liver metastases are generally diagnosed through liver function tests, CT scans, and ultrasound scans. A liver biopsy may be required if there is insufficient evidence of levels of oestrogen or human epidermal growth fact receptor-2 (HER-2). Liver metastases are generally treated with chemotherapy, hormone therapy or targeted therapies. Surgery is generally not employed because of the multifocal nature of liver metastases. Occasionally selective radiotherapy may be used or cryoablation.
Systemic treatments for metastatic breast cancer are generally either chemotherapy or hormone treatments.
Because the side effects of chemotherapy can be very severe (nausea, vomiting, hair loss, diarrhoea, neutropenia) the treatment needs to be finely balanced to enable maximum quality of life and effectiveness. These drugs may include: docetaxel, cyclophosphamide, paclitaxel, gemcitabine, epirubicin, doxorubicin (all IV) or oral drugs: capecitabine or vinorelbine.
Most breast cancers are sensitive to hormones; metastatic breast cancer that is oestrogen receptor positive and not immediately life-threatening is suitable for hormone therapy.
Tamoxifen is an anti-oestrogen which blocks the action of oestrogen in the tumour cells; this is suitable for women who are pre or post-menopause. Aromatase inhibitors are only licensed for post-menopausal women. Goserelin implants may be administered to reduce circulating oestrogen, this can also be achieved by surgical ovarian ablation or radiotherapy. This is generally a successful and well-tolerated therapy, although there are side effects including vaginal dryness, hot flushes, weight gain and problems with body image.