Breast cancer

Breast cancer is cancer of breast tissue. Worldwide, it is the commonest form of cancer in females. More than 99% of cases occur in women, but men can also develop breast cancer (the relative risk of developing breast cancer in a female versus a male is more than 100; see sex and illness).

Epidemiology

Overall, it has been estimated that women have about a 1 in 10 lifetime risk of developing breast cancer. 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, white and black women 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 and late menopause, and taking hormone therapy.

The probability of breast cancer rises with age but breast cancer tends to be more aggressive when it occurs in younger women.

Genetics

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.

Diagnosis

Breast cancer can be detected by a woman when washing, by her partner during foreplay, by formal breast self-examination or by screening 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.

Treatment

The breast lump must be excised either as a local operation called lumpectomy or as a larger operation called mastectomy. 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 biopsy 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:

1. after a lumpectomy, the high local recurrence risk (~40%) is reduced by radiotherapy to the breast
2. if the lymph nodes are positive, the high mortality risk (30-80%) is reduced by systemic treatment (which could be either hormones or chemotherapy).
3. in young patients, the most useful systemic therapy is chemotherapy (usually regimens such as CMF, AC and/or taxol)
4. in old patients, the most useful systemic therapy is hormone therapy (tamoxifen)
5. in old patients, chemotherapy has increasing side effects as the patients passes 65
6. in patients with estrogen receptor negative tumours, the most useful systemic therapy is chemotherapy
7. in patients with estrogen receptor positive tumours, the most useful systemic therapy is hormone therapy

For some early tumours, systemic treatments may not be recommended. After mastectomy, radiotherapy may not be recommended. For advanced tumours, there is an established role for all three modalities of treatment (surgery, radiation, systemic therapy) as the combination produces the best results.

Prognosis

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.