Breast cancer is cancer of breast tissue. Worldwide, it is the most common form of cancer in females.
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Overall, it has been estimated that women have about a 1 in 10 lifetime risk of developing breast cancer. Men can also develop breast cancer, although their risk is less than 1 in 1000 (see sex and illness). This risk is modified by many different factors. In some families, there is a strong inherited risk of breast cancer. Some racial groups have a higher risk of developing breast cancer - notably, women of European and African descent have been noted to have a higher rate of breast cancer than women of Asian origin.
Other established risk factors include having no children, having the first child later, not breastfeeding, having early menarche (the first menstrual period), having late menopause, and taking hormone replacement therapy. (However, the National Cancer Institute notes that the benefits of hormone replacement therapy generally outweighs the risks .)
The probability of breast cancer rises with age but breast cancer tends to be more aggressive when it occurs in younger women.
Two genes, BRCA1 and BRCA2, have been linked to the familial form of breast cancer. Women in families expressing these genes have a much higher risk of developing breast cancer than women who do not.
Breast cancer may be detected manually (e.g. by breast self-examination) or by mammography. Only mammography has been proven to reduce mortality from breast cancer.
On finding a lump, the next step should be to visit the family doctor. The usual investigations should include an examination and mammogram. An ultrasound scan and biopsy may also be undertaken. If there is suspicion or confirmation of problems at this stage, the patient will be seen by a surgeon. Many large centres have 'breast' surgeons, and even in centres with 2-3 surgeons it is probably better to see the one with an interest in breast cancer.
If breast cancer is confirmed by biopsy or by open excision, the diagnosis has been established. The second phase is then tumour staging which deals with questions of how big, how much and how far.
(Note: consult a trustworthy site such as www.breastcancer.org for more complete and up-to-date information.)
The breast lump must be excised either as a local operation called lumpectomy (removal of the lump only) or as a larger operation called mastectomy (removal of the entire breast). In either case the surgeon must establish that the cancer has been completely excised (clear margins) by the operation. If the lumpectomy operation does not have clear margins, then the operation should be repeated until clear.
The lymph nodes in the axilla also need to be studied. In the past, large axillary operations took out 10-40 nodes to establish whether cancer had spread. More recently sentinel lymph node dissection has become popular as it has far fewer side effects.
In some cases at high risk, CT scans, chest X-rays and blood tests will also be advisable to look for any metastasis or secondary cancer that has spread a long way from the site of the primary tumour.
Oncologists then assign a TNM code as a shorthand categorisation which in turn determines treatment recommendations. Some biological features of the cancer such as estrogen receptor and HER2-neu oncogene are also determined as they also affect treatment recommendations.
At present, the treatment recommendations follow this pattern:
- after a lumpectomy, the high local recurrence risk (~40%) is reduced by radiation therapy to the breast
- if the lymph nodes are positive, the high mortality risk (30-80%) is reduced by systemic treatment (which could be either hormones or chemotherapy).
- in young patients, the most useful systemic therapy is chemotherapy (usually regimens such as CMF, AC and/or taxol)
- in older patients, the most useful systemic therapy is hormone therapy (tamoxifen)
- chemotherapy has increasing side effects as the patients passes 65
- in patients with estrogen receptor negative tumours, the most useful systemic therapy is chemotherapy
- in patients with estrogen receptor positive tumours, the most useful systemic therapy is hormone therapy
Long term outcome depends on the staging of the breast cancer at diagnosis and how well the cancer has been treated. Generally speaking, the earlier the cancer is detected, the better the prognosis becomes.