Breast Cancer Risk Factors

What Are the Common Risk Factors for Breast Cancer?


Simply being a woman is the main risk factor for developing breast cancer. Although women have many more breast cells than men, the main reason they develop breast cancer more often is because their breast cells are constantly exposed to the female hormones estrogen and progesterone, which promote cell growth. Men can develop breast cancer, but this disease is about 100 times more common among women than men.


Your risk of developing breast cancer increases as you age. About 2 out of 3 invasive breast cancers are found in women age 55 or older.

Family History

The chance of developing breast cancer increases if a close relative, either male or female, had breast cancer. About 20 to 30 percent of women with breast cancer have a family member with the disease.

Gene Changes

Breast cancer is sometimes caused by inherited gene changes. The most common are in the BRCA1 and BRCA2 genes which cause a significantly increased risk for breast and ovarian cancer.

Previous Breast Cancer

A woman with cancer in one breast is three to four times more likely to develop a new cancer in the other breast, or in another part of the same breast. This is different from a recurrence, or return of the first cancer.

Benign Breast Biopsy

About 80 percent of all breast changes that are biopsied, or tested, are found to be benign, or not cancerous. But, some of these benign breast conditions are linked to an increase in breast cancer risk.

Radiation Exposure

Receiving radiation therapy to the chest between the ages of 10 and 30 can increase the risk of breast cancer. The risk of developing breast cancer appears to be highest if the radiation was given during adolescence, when the breasts are still developing.

Hormone Exposure

Use of hormones after menopause called hormone replacement therapy may increase the risk for developing breast cancer.