Breast Cancer Risk Factors

Institutes & Services > Women's Services

One of every eight women will develop breast cancer during their lifetime.

Breast Cancer Risk Factors

A risk factor is anything that increases someone’s chance of getting a disease. Not all cancers have the same risk factors; they vary by type of cancer.

Keep in mind that if you have one or more risk factors for breast cancer, it doesn’t necessarily mean that you will get cancer. Some women have one or more breast cancer risk factors but never develop the disease. And most women who do have breast cancer have no recognizable risk factor.

Significantly Higher Risk

Previous breast cancer 

  • A woman who has had breast cancer in one breast is 3 to 4 times more likely to develop a new breast cancer, unrelated to the first cancer, in the other breast or in the same breast but in another section. This is not the same as a recurrence of the earlier breast cancer.

Genetics 

  • Carriers of familial breast cancer genes (BRCA1 or BRCA2) are at higher risk. Those women who have inherited an alteration of one of these genes have up to an 85% chance of getting breast cancer in their lifetime.
  • See also: The Role of Genetics in Breast Cancer

Breast lesions (wounds or areas that have been damaged by injury or disease)

  • An earlier biopsy of the breast that identified atypical tissue growth or lobular carcinoma in situ raises a woman’s risk of developing breast cancer by 4 to 5 times.

Moderately higher risk

Aging

  • The risk of developing breast cancer rises as you grow older.
  • Approximately 77% of women who receive breast cancer diagnoses each year are older than 50 and nearly half of them are 65 and older.
  • Women aged 40 to 49 have a 1 in 68 risk, while the risk for those 50 to 59 climbs to 1 in 37.

Direct family history

  • Women who have a direct relative mother, sister or daughter with breast cancer have a higher risk.  The risk rises more if the mother, sister or daughter got breast cancer before menopause and had cancer in both breasts.
  • One first-degree relative with breast cancer almost doubles the risk.
  • Having two first-degree relatives raises the risk to five times.
  • A male blood relative with breast cancer also raises a woman’s risk.
  • See also: The Role of Genetics in Breast Cancer

Previous abnormal breast biopsy

  • Women with these conditions have a slightly higher risk:
    • Fibro adenomas with complex features
    • Hyperplasia with atypia (unusual features)
    • Sclerosing  adenosis (characterized by multiple small, lumps, fibrous tissue, and sometimes small cysts)
    • Solitary papilloma (small breast lump, usually near the nipple)
     

Too much radiation

  • Women who receive large doses of radiation before they are 30 are at risk for breast cancer.

Slightly higher risk

Distant family history 

  • Breast cancer in non-direct relatives such as aunts, grandmothers, or cousins

Age at childbirth

  • Women who have their first child after age 35 or have never had children
  • Early menstruation (before age 12)
  • Late menopause (after age 55)

Body weight

  • Especially after menopause, excess weight, particularly around the waist, with too much fat and calorie intake

Other cancers in the family

  • Family history of ovarian, cervical, uterine or colon cancer

Heritage

  • Women whose relatives were Ashkenazi (Eastern and Central European Jews)

Alcohol

  • Women who have more than 1 alcoholic drink per day have a slight increase in breast cancer risk.
  • Women who have 2 to 5 alcoholic drinks per day have about 1 ½ times the risk of women who do not drink.

Race

  • Caucasian women have a slightly higher risk compared to African American, Asian, Hispanic and Native American women.
  • African American women are more likely than Caucasians to have breast cancer before age 40.

Hormone Replacement Therapy (HRT)

  • Women who have taken combined estrogen with progesterone over the long term have an increased risk compared to those who have not taken HRT. The risk may return to normal levels after HRT is stopped for 5 years or longer.

Low Risk

  • Becoming pregnant before age 18
  • Going through menopause early
  • Having ovaries removed before age 37
  • Women who have breastfed have a lower risk of developing breast cancer.

These factors are not related to breast cancer:

  • Fibrocystic breast changes
  • Multiple pregnancies
  • Coffee or other caffeine
  • Anti-perspirants
  • Underwire bras
  • Miscarriage or abortion
  • Breast implants

Still inconclusive

Research continues to investigate the possible effects on breast cancer risk of:

  • Smoking
  • Lack of exercise
  • Pollution in the environment
  • High-fat diets

Some studies suggest that use of birth control pills may be associated with an increased risk of getting breast cancer. The risk appears to go away after women stop using the pills for 10 or more years. Other research has found no connection between birth control pills and breast cancer.

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