Age

The risk of breast cancer increases with age. It is most common in people over age 50, although it must be kept in mind that 45% of cases are diagnosed in patients over 65.

Hormonal factors

• Exposure to hormones such as estrogen or progesterone increase the risk of breast cancer appearing. Two examples of increased exposure to hormones occur in hormone replacement therapy and contraceptive pills (this risk is reduce as soon as you stop taking the pills).
• Not having children or having them after age 30.
• Not having breastfed or only breastfeeding for less than a year.
• Having your first period (menarche) at an early age and/or entering menopause at an older-than-normal age.

Alcohol and tobacco

Drinking substantial amounts of alcohol and heavy smoking over a long period of time increases the risk of developing breast cancer.

Obesity

Excess weight may increase the risk of developing breast cancer. This may be due to changes in hormones that happen when a person is overweight.

Family history

Only a small percentage of women with breast cancer (5-10 %) have the genes that increase the risk of having the disease. These genes are called BRCA1 and BRCA2.

Most women who are diagnosed with breast cancer do not have a family history of the disease. When taking into account family history, the chances of having breast cancer increase when:

• Other family members have been diagnosed with breast or ovarian cancer.
• When these are members of your immediate family, such as your mother or sister.
• Diagnosis at an early age.

Precancerous conditions

Precancerous lesions in the breast may increase the risk of breast cancer appearing. One example of this is atypical ductal hyperplasia.

Radiotherapy on the breasts at an early age.

The risk of breast cancer increases if you have had previous radiotherapy.