Breast cancer

Updated 15 November 2017

Risk factors for breast cancer

The exact cause of breast cancer remains unknown although research has discovered a number of factors that can increase your risk of developing cancer of the breast.

Just as in the case of many other cancers, the exact cause of breast cancer is unknown. Research into this topic is ongoing. It is thought that breast cancer could be caused by several genetic, nutritional, environmental and hormonal factors.

What is certain is that worldwide, the incidence of breast cancer is rising. But because of early detection, the rate of death from breast cancer has not increased.

Having the risk factors below does not mean that you will develop breast cancer. While some risk factors, such as smoking and drinking, can be avoided, others such as age and genetic inheritance cannot.

While no definitive information is available on exact causes, researchers have found the following  factors to increase the risk of a woman being diagnosed with breast cancer:

Age at first pregnancy. Age at the time of first pregnancy is significant in that women who first fell pregnant after the age of 30, or who have never had children, are at an increased risk.

Age. Women over 50 account for 77 of breast cancer cases.

Early onset of menstruation. Women whose first period was before the age of 12.

Young smokers. Women who started to smoke within five years of the onset of their first period.

History of cancer. Previous breast, ovarian, colon or uterine cancer diagnosis carries an increased risk.

Dense breast tissue. This can also complicate the detection of breast tumours.

Genetic inheritance. If a mother or sister was diagnosed with breast cancer before menopause, a woman’s risk is doubled.

High exposure to oestrogen. Certain oral contraceptives, when taken over long periods of time may increase the risk.

Radiation treatment. Radiation treatment to the chest area before the age of 30 plays a role.

Heavy drinking. Five or more drinks per day increases the risk. One drink a day carries a smaller risk.

A history of benign breast lumps and tumours. This is especially true for younger women.

Hormone replacement therapy (HRT). Being on HRT for longer than 8 years definitely increases the risk.

Menopause after age 55. Late onset of menopause is a risk factor.

Obesity. Severe overweight seems to play a role especially if coupled with a high-fat diet.

Social status. Breast cancer is more common in women from higher socio-economic groups, women who are unmarried and women who live in urban areas.

Read more:
Symptoms of breast cancer

Treating breast cancer

Sources:; C Health; National Breast Cancer


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Dr Gudgeon qualified in Birmingham, England, in 1968. She has more than 40 years experience in oncology, and in 1994 she founded her practice, Cape Breast Care, where she treats benign and malignant breast cancers. Dr Boeddinghaus obtained her qualification at UCT Medical School in 1994 and her MRCP in London in 1998. She has worked extensively in the field of oncology and has a special interest in the hormonal management of breast cancer. She now works with Dr Gudgeon at Cape Breast Care. Read more.

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