What we know
Having one or more risk factors does not mean that a person will develop breast cancer, but it might increase their chance of developing breast cancer. Some risk factors like gender, age or race, cannot be changed.
The main risk factors for developing breast cancer appear to be:
- Being female. Men can get breast cancer but it is rare and accounts for less than 1% of all breast cancers;
- Having a strong family history of breast cancer. Having said that, the majority of people who are diagnosed have no known family history;
- Inheriting a faulty gene (a gene mutation) that increases the risk of breast cancer. Having said that, only 10% of breast cancer is genetically linked; and
- Having previously been diagnosed with breast cancer or DCIS.
Other factors that seem to slightly increase a woman’s risk of developing breast cancer include:
- Starting menstruation at a relatively early age (before 12 years);
- Starting menopause at a relatively late age (after 55 years);
- Not having children or having a first child after 30 years of age;
- Not breastfeeding – the more months spent breastfeeding, the lower the risk of developing breast cancer;
- Taking combined Hormone Replacement Therapy (HRT) after menopause, especially when taken for 5 years or longer;
- Gaining a lot of weight in adulthood, especially after menopause;
- Drinking alcohol (more than 2 standard drinks a day);
- Previously having been diagnosed with lobular carcinoma in situ (LCIS) or atypical hyperplasia;
- Smoking in younger premenopausal women; and
- Eating processed meats.