Risk factors for breast cancer

Each year, about 50,000 women are diagnosed with breast cancer in the UK. It is more common in women who are aged 50 and over, but it can also affect younger women. Improvements in treatment mean more women are surviving breast cancer.

The exact cause of breast cancer is unknown. But certain things called risk factors can increase your chance of developing it. Having one or more risk factors doesn’t mean you will definitely get cancer. Equally, if you don’t have any risk factors, it doesn’t mean you won’t get breast cancer.

Some risk factors for breast cancer include:

  • getting older
  • having had breast cancer or some other breast conditions before
  • lifestyle factors, for example smoking or drinking alcohol
  • a family history of breast cancer, or related cancers such as ovarian cancer.

Breast cancer is likely to be caused by a combination of different risk factors, rather than just one.

Breast cancer and some breast conditions

Your risk is increased if you have had breast cancer before. This includes ductal carcinoma in situ. Having the following breast conditions can also increase your risk:

  • lobular carcinoma in situ (LCIS)
  • atypical ductal hyperplasia – there are slightly abnormal cells in the milk ducts in a small area of the breast
  • dense breast tissue – when the breast is mostly made up of glandular and connective tissue and has very little fatty tissue.

Radiotherapy to the chest at a young age

Women who have had radiotherapy to the chest at an early age (for example to treat Hodgkin lymphoma) have an increased risk of breast cancer.

Hormonal factors

The female hormones oestrogen and progesterone can affect your breast cancer risk. Factors that can increase your risk include:

  • Taking hormone replacement therapy (HRT) – particularly if you are taking combined HRT (oestrogen and progesterone). When you stop HRT, your risk reduces again.
  • Not having children.
  • Having children after the age of 30.
  • Not breastfeeding your children, or breastfeeding for less than a year in total.
  • Starting your periods early (under the age of 12) or having a late menopause (after the age of 50).
  • Taking the contraceptive pill, although the risk reduces if you stop taking it.

Back to Potential causes of breast cancer

Hormonal factors

Your exposure to the hormones oestrogen and progesterone can affect your risk of developing breast cancer.

Genetic factors

There are sometimes genetic links between cancers in the same family.