Risk Factors for Breast Cancer

Age: The chances of developing breast cancer increases with age. The disease rarely affects women younger than 25 years of age, whereas close to 80% of breast cancers occur in women older than age 50. At age 40, there is a one in 252 chance of developing breast cancer. By age 85, the chances are one in eight.

A personal history of breast cancer: If an individual has had breast cancer in one breast, there is an increased risk of developing cancer in the other breast.

Family history: If the individual's mother, sister, daughter or male relative has had breast cancer, ovarian cancer, or both, the risk of developing breast cancer is doubled. In general, the more relatives one has with breast cancer that were premenopausal at the time of diagnosis, the higher the risk.

Genetic predisposition: Between 5 and 10% of breast cancers are inherited. Defects in one of several genes, especially BRCA1 or BRCA2, put the individual at a greater risk for developing breast, ovarian and colon cancers. Usually these genes help prevent cancer by making proteins that keep cells from growing abnormally, but if they are mutated, then the genes aren't effective at protecting the individual from cancer.

Radiation exposure: Radiation treatments to the chest experienced as a child or young adult may increase in the risk of developing breast cancer later in life. The younger the individual was when they received the treatments the greater the risk.

Excess weight: The relationship between excess weight and breast cancer is complex. In general, weighing more than what is normal for the patient's age and height increases the risk of breast cancer, especially if the patient has gained the weight as an adult or in postmenopause. The risk is even greater if the excess fat is in the upper part of the body. Although women usually have more fat in their thighs and buttocks, they tend to gain weight in their abdomens in their 30s, which can increase their risk of developing breast cancer.

Exposure to estrogen: The longer an individual is exposed to estrogen, the greater the risk of breast cancer. In general, if an individual has a late menopause (after age 55) or early menses (before age 12), there is a slightly higher risk of developing breast cancer. Women who never had children or whose first pregnancy occurred when they were age 35 or older also have an increased risk of developing breast cancer.

Race: Caucasian women are more likely to develop breast cancer than African-American or Hispanic women. However, African-American women are more likely to die of the disease because their cancers are found at a more advanced stage. Although some studies show that African-American women may have more aggressive tumors, socioeconomic factors may enter the picture also. Women of all races with incomes below the poverty level are often diagnosed with late-stage breast cancer, and are more likely to die of the disease than women with higher incomes. Low-income women don't usually receive the routine medical care that would allow breast cancer to be discovered earlier.

Hormone therapy: A study sponsored by the National Institutes of Health (NIH) in June 2002 was halted as researchers reported that hormone therapy, once considered standard treatment for menopausal symptoms, actually posed more health risks than benefits. Along with an increase in cardiovascular disease and uterine cancer, there was a slightly higher risk of breast cancer for women taking the particular combination of hormone therapy (estrogen plus progestin) used in the study. In addition, combination hormone therapy can make malignant tumors harder to detect on mammograms, leading to cancers that are diagnosed at more advanced stages when they're more difficult to treat.

Birth control pills: The hormone therapy studies have raised questions about the relationship between birth control pills and breast cancer. Studies have reported that women who are currently using birth control or have used them in the past 10 years are at a slightly increased risk for having breast cancer in the next 10 years. These cancers tend to be localized to the breast and are less clinically advanced than the cancers diagnosed in women who never used birth control pills.

Smoking: Studies have found that smoking does increase the incidence of breast cancer in those with the genetic predisposition. More than 30 carcinogenic chemicals are present in tobacco smoke; many of which are fat-soluble, resistant to metabolism and can be stored in breast adipose tissue. A study published in 2001 found that smoking significantly increases the risk of breast cancer in women with a family history of breast and ovarian cancers. A more recent study found that exposure to secondhand smoke also increases the risk of breast cancer in premenopausal women. Researchers hypothesize that higher estrogen levels combined with the cancer-causing agents in tobacco spark the development of breast tumors.

Other carcinogens: Polycyclic aromatic hydrocarbons are chemicals found mainly in cigarette smoke and charred red meat. Studies have shown that exposure to these chemicals can significantly increases the chances of developing breast cancer. Exposure to certain pesticides may also increase the risk.

Excessive use of alcohol: Women who consume more than one alcoholic drink a day have about a 20% greater risk of breast cancer than women who don't drink. The National Cancer Institute recommends limiting alcohol intake to no more than one drink per day.

Precancerous breast changes (atypical hyperplasia, carcinoma in situ): These changes are often discovered only after a breast biopsy is performed, and they can double the risk of developing breast cancer.

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