Breast Cancer Risk Factors

Breast cancer risk factors are factors about an individual which may be associated with an increased risk of developing the disease at some point. If you have one or more of the risk factors for breast cancer it does not mean you will necessearily get breast cancer, just that your risk of it is increased relative to the general population, statistically.

There are two general classes of risk factors, those that you can change and those that you can't. Non-modifiable risk factors include those things which are not changeable. In other words, these are things related to you individually that you cannot affect. For example, your age, gender, ethnicity, genetics and so on are all examples. Modifiable risk factors are factors which you can change. They include lifestyle choices and habits which may impact your risk for cancer. For example, smoking is a strong modifiable risk factor for lung cancer. You can modify it by quitting smoking, which reduces your risk.

Below you can read about some of the most common and best understood breast cancer risk factors. They are split into non-modifiable and modifiable breast cancer risk factors.

Non-Modifiable Breast Cancer Risk Factors
(Risk Factors You Can't Change)

Female Gender: Men can develop breast cancer but it is quite rare. Women are at much higher risk for two primary reasons. For one, they have a larger amount of breast tissue. Additionally, that breast tissue is exposed to the growth-stimulating effects of the hormones estrogen and progesterone throughout their lives whereas men have very low levels of these hormones. Clearly, this is one of the strongest breast cancer risk factors.

Aging: As with many cancers, breast cancer risk increases as you get older. While it can occur in younger individuals, particularly those with strong genetic and familial risks, the risk rises dramatically after the age of around 55 years.

Genetic Risk Factors (BRCA1 and BRCA2): There are probably several genes which impact the risk for developing breast cancer. These are passed through heredity, so getting these genes from a partent increases your risk of developing cancer. The most well-studied of these genes are the BRCA1 and BRCA2 genes. Inhereting one of these abnormal gene types increases the risk for breast cancer dramatically and women tend to develop cancers at a younger age. Although they only represent a small subset of the general population it is a profound risk and therefore is one of the most important breast cancer risk factors. You can be tested for these genes if you have reason to believe they may run in your family. There are a number of other genes (ATM, p53, PTEN, etc.) which have been implicated in breast cancer development as well but none are as common or as strong an association as the BRCA genes.

Family History of Breast Cancer: If you have any one first-degree relative (meaning someone in your immediate family, such as a mother, sister or daughter) with breast cancer, it doubles your risk of developing the disease, roughly. More family members with the disease further increase your risk. While some of these connections can be explained by sharing an abnormal gene (see above) sore are less clear and may be due to multiple genes. While as many of a third of all women with breast cancer have some family history of the disease, 70 to 80% do not have any family history.

Personal History of Breast Cancer: In a woman who has previously had breast cancer, their risk for developing another cancer in the same or other breast is considerably higher.

Race/Ethnicity: Race and ethnicity can be another breast cancer risk factor in different ways. While caucasian women have a slightly higher rare of breast cancer overall, they tend to be less aggressive on average. On the other hand, African-American women, while their overall risk is lower, are at a higher risk of dying from breast cancer since they tend to develop more aggressive forms of the disease. Asian, Hispanic and Native-American women all have a slightly lower risk of developing breast cancer and also of dying from the disease.

Dense Breast Tissue: Some women have denser breast tissue than others. This means they have more breast gland tissue, which is the part prone to developing cancer, and less fatty tissue. This increases their risk for cancer somewhat. It also makes it more difficult to detect since mammograms on very dense breast tissue can have a hard time identifying tumors.

Number of Menstrual Periods: Overall, lifetime exposure to estrogen and progesterone seem to be associated with risk for breast cancer. Women who have had more menstrual periods, either because they started menstrating earlier (before age 12 typically) and/or went through menopause (when menstrual cycles stop) at a later age (typically after age 55), are at slightly greater risk of developing breast cancer.

Previous Chest Radiation Exposure: The breast tissue appears to be sensitive to the cancer-causing effects of radiation. Women who have had radiation to their chest in childhood or young adulthood are at slightly higher risk. Examples include therapeutic radiation to the chest for another cancer such as lymphoma.

Diethylstilbestrol Exposure: Diethylstilbestrol (DES) was a drug which was used in the 1940's through the 1960's. It was given to pregnant women and was though to help decrease the risk of miscarraige. However, it was later found the the drug increased the risk for breast cancer, both in the women as well as in the fetus. Therefore, women who's mother took DES during their pregnancy are at risk of developing breast cancer.

Modifiable Breast Cancer Risk Factors
(Risk Factors Related to Lifestyle)

Not Having Children or Later Childbirth: Women who do not have children until later in life or who never have children are at a slightly increased risk of breast cancer than those who have had multiple pregnancies or were pregnant at a young age. Although this effect isn't completely understood, it is thought to be related to the number of menstrual cycles, and thus exposure to estrogen and progesterone, a woman has in her life (see above).

Oral Contraceptive Use: Studies have shown a slight increased risk of breast cancer in women who are currently using oral contraceptives (birth control pills). However, this effect appears to reverse over time if the woman stops using the pills.

Post-Menopausal Hormone Therapy: Hormone replacement therapy in post-menopausal women increases their exposure to estrogen and/or progesterone. While the benefits of these treatments is still debated, it appears that some use of hormone replacement therapy is a breast cancer risk factor. This is strongest in women using a combined therapy which includes both an estrogen and a progesterone. Estrogen only therapy does not appear to increase the risk significantly unless used long term.

Not Breast Feeding: Breast-feeding may lower breast cancer risk slightly, especially with extended breast feeding (1-1/2 to 2 years). This may be related to the fact that these women tend to have less menstrual cycles since they do not typically have periods during lactation.

Alcohol: Although moderate alcohol consumption has been shown in some studies to reduce the risk of some diseases, this does not appear to be the case for breast cancer. In fact, alcohol appears to increase the risk of breast cancer. The level of risk seems to increase with increased consumption of alcohol.

Obesity: Some studies have shown a correlation with obesity after menopause with breast cancer risk but the connection is not clearly understood and appears complex. For example, women appear to be at more risk if they gained weight later in life as oppossed to women who have always been overweight.

Physical Activity: Studies have shown that increasing physical activity may lower your risk for developing breast cancer.