Breast cancer: Overview of risks

In the UK, breast cancer is the most common type of cancer among women. Around one in nine women are affected by breats cancer in their lifetime. Approximately 46,000 cases are diagnosed every year, most often in women who are over 50 years old.

What are the risk factors of breast cancer?

A risk factor is anything that increases a person's chance of getting a disease. Different cancers have different risk factors.

But having a cancer risk factor, or even several of them, does not necessarily mean that a person will get cancer. Some women with one or more breast cancer risk factors never develop it, while most women with breast cancer have no apparent risk factors.

Significantly higher risk

A woman with a history of cancer in one breast has a much greater chance of developing a new breast cancer, unrelated to the first one, in the other breast or in another part of the same breast. This is different from a recurrence of the previous breast cancer.

Moderately higher risk

• Getting older. Your risk for breast cancer increases as you age. About 75% of women diagnosed with breast cancer each year are over age 50, and about 90% of breast cancer deaths are in women aged 50 or older.
• Direct family history. Having a mother, sister or daughter (first degree relative) who has breast cancer puts you at higher risk for the disease. The risk is even greater if your relative developed breast cancer before menopause and had cancer in both breasts. Having one first degree relative with breast cancer approximately doubles a woman's risk. Having a male blood relative with breast cancer will also increase a woman's risk of the disease.
• Genetics. Carriers of alterations in either of two familial breast cancer genes called BRCA1 or BRCA2 are at higher risk. Women with an inherited alteration in either of these genes have up to an 65% chance of developing breast cancer by the age of 70. There are rarer genes, such as TP53 and PTEN which can also increase risk of breast cancer.
• Breast lesions. A previous breast biopsy result of atypical hyperplasia increases a woman's breast cancer risk by two to four times.

Slightly higher risk

• Distant family history. This refers to breast cancer in more distant relatives such as aunts, grandmothers and cousins.
• Previous abnormal breast biopsy. Women with earlier biopsies showing any of the following have a slight increased risk: fibroadenomas with complex features, hyperplasia without atypia, sclerosing adenosis, and solitary papilloma.
• Age at childbirth. Having your first child after age 30 or never having children puts you at higher risk.
• Early menstruation. Your risk increases if your periods began before the age of 11.
• Late menopause. If you begin the menopause after age 55, your risk increases.
• Weight. Being overweight (especially in the waist), with excess calories and fat intake, increases your risk, especially after menopause.
• Excessive radiation. This is especially true for women who were given radiation for postpartum mastitis, received prolonged fluoroscopic X-rays for tuberculosis or who were exposed to a large amount of radiation before age 30, usually as treatment for cancers such as lymphoma.
• Other cancer in the family. A family history of cancer of the ovaries, cervix, uterus or colon increases your risk.
• Heritage. Women born in North America and northern Europe are at increased risk.
• Alcohol. Use of alcohol is linked to increased risk of developing breast cancer. Alcohol is also known to increase the risk of developing cancers of the mouth, throat, and oesophagus.
• Race. White  women are at a slightly higher risk of developing breast cancer than are African, Asian and Hispanic women.
• Hormone Replacement Therapy(HRT). Long term use of combined oestrogen and progesterone increases the risk of breast cancer. The risk returns to the same as that of a woman who has never used HRT five years after a woman stops using HRT.
• Combined Oral Contraceptive Pill.   Cancer Research UK says there seems to be a small increase in risk while you are taking the pill, but this goes back to a normal level of risk 10 years after you've stopped taking it.  However the pill seems to reduce the risk of some other cancers, including ovarian cancer.
  
  Low risk

• Pregnancy before age 18.
• Early onset of menopause.
• Surgical removal of the ovaries before age 37.

Factors not related to breast cancer

• Fibrocystic breast changes.
• Multiple pregnancies.
• Coffee or caffeine intake.
• Antiperspirants.
• Underwire bras.
• Abortion or miscarriage.
• Breast implants.

Scientists are still investigating whether breastfeeding, smoking, high fat diets, lack of exercise and environmental pollution increase breast cancer risk.