Cancer

Breast Cancer: Causes and Prevention

Jessica Evert, MD, edited by Benjamin McDonald, MD

The causes of breast cancer are not yet definitively known. However, extensive research efforts have uncovered various risk factors that are associated with increased incidence of breast cancer in women. Though some of these risk factors are unavoidable and uncontrollable, some of them are very avoidable, making it possible for people to take action so as to minimize their cancer risk. Even a minimized risk is still a risk, however. There is no way to pre-determine whether a person will get breast cancer until they have either been diagnosed with it or they have lived a breast-cancer free lifetime.

Some of the risk factors for breast cancer that are difficult or impossible to control include:

  • Age. As women age their chance of getting breast cancer increase. The majority of breast cancer cases are diagnosed in women over the age of 50. Women over the age of 20 should get clinical (by a doctor or other health professional) breast exams at least every three years according to the American Cancer Society.  During the first clinical breast exam your physician should explain to you the potential benefits and limitations of breast self exam and instruct you on appropriate technique.  The American Cancer Society now says that women need not perform a BSE every month if they do not wish to.  However, it is important for all women to be vigilant of any changes in their breasts and to report any changes to their physician as soon as possible.  Asymptomatic women over the age of 40 should receive clinical breast exams during their yearly health maintenance exam (ACS, 2009). As a general rule asymptomatic women in their 40s and older should get yearly mammograms to check for breast cancer. The frequency with which someone should have mammograms performed should be determined with the input of a physician.

  • Family and genetic history. Some cases of breast cancer are known to have been caused as a result of genetic mutation. Gene mutations can be inherited from parents and can also occur in otherwise healthy people in response to environmental toxins. Having a close relative on either side of your family who has breast cancer will, in general, increase your risk of contracting breast cancer.  This is particularly true if the relative is what is called "first degree" meaning your sister or mother.  In general, the more first degree relatives that have had breast cancer the more likely you are to develop breast cancer as well.

  • BRCA gene mutation.  Recent advances in genetic mapping have discovered a gene mutation that increases the risk of certain female cancers in women with the mutation.  The two main breast and ovarian cancer susceptibility genes are known as BRCA1 and BRCA2.  I selected women who have extensive family history of breast cancer or ovarian cancer it may be beneficial to be tested for the mutations at an early age.  This would allow affected individuals to make informed decisions about prophylactic (preventative) surgery before they contract either type of cancer.  Fortunately, it is thought that only 5-10% of breast cancer cases are caused by these mutations and that the mutations are only present in about 1% of the general population (ACS, 2009).  For this reason the US Preventive Services Task Force recommends that only women with a very strong family history of breast cancer be evaluated for the BRCA mutations (USPSTF, 2005).  The American Cancer Society states that women with the BRCA1 mutation have a 57% chance of getting breast cancer by age 70 while those with the BRCA2 mutation have a 49% chance of getting breast cancer by age 70 (ACS, 2009). 

  • Previous breast cancer. A woman who previously had breast cancer and has been cured has a greater chance for having a new breast cancer episode occur than is a woman who never had the disease. New tumors appearing inside someone with a previous history of cancer who has been cancer free are not necessarily related to or caused by old eradicated tumors. Instead, new tumors can form spontaneously in vulnerable persons.

  • Race. Hispanic and Asian women have lower risk for getting breast cancer than do Caucasian and African American women. In fact, Caucasian women are at the highest risk of getting the disease compared to women of other racial backgrounds. African American women, however, are historically the most likely to die from breast cancer because, in general, their tumors are diagnosed at a later stage. Why there is a failure to identify tumors in Aafrican Aamerican women until later in their development is not clear at this time. It may occur because, as a group, these women have less access to healthcare, or possibly because they are less likely as a group to seek healthcare.  Research is ongoing in this area to determine the cause of this alarming disparity.

  • Previous benign tumor biopsy results. Women who have had previous biopsy that has found a benign (non-cancerous) tumor in the breast are at a greater risk for malignant breast tumors in the future. However, the occurrence of cysts in the breast does not increase the risk for future breast cancer.

  • Prior radiation treatment in the chest area. Women who receive prior radiation treatment directed at their chest area for any reason are at a heightened risk for future breast cancer compared to women who do not receive radiation treatment. The earlier in life women are exposed to chest-targeted radiation treatment, the higher their later risk for breast cancer.

  • Menstrual Cycles. Women who begin menopause after the age of 50 or who had their first menstrual cycle before age 12 run a slightly higher risk for breast cancer than women whose menstrual cycles started after age 12 and end prior to age 50.  This is due to prolonged exposure to high levels of certain reproductive hormones.

While the above risk factors for breast cancer are difficult or impossible to avoid, there are also numerous risk factors for breast cancer that can be avoided by making healthy lifestyle choices. While choosing a healthy lifestyle may not always be simple or easy, making such lifestyle changes can help you lower your cancer risk with regard to the following risk factors:

  • Use of Birth Control Pills. Some studies have shown that women who use birth control pills are at a slightly increased risk for breast cancer. However, any relationship between breast cancer and birth control pill use remains controversial at this time, pending further research. It's not all bad news. While oral contraceptives (birth control pills) may slightly increase risk of breast cancer, they appear to reduce the risk of other types of female cancers. Consult with your doctor about the risks and benefits of birth control pills if you have concerns about breast cancer risk.

  • Not Having Children. Women who have their first child after the age of 30 or who have never had children run a slightly higher risk for contracting breast cancer than do women who give birth before reaching age 30. This is again due to more prolonged exposure to reproductive hormones.  Be this as it may, a decision as important as whether or not to have children should not be influenced by the small reduction or elevation in risk for breast cancer it may carry.

  • Hormone Replacement Therapy. Hormone replacement therapy (HRT) is sometimes prescribed to women as a means of alleviating discomfort associated with menopause. Research indicates that women who have received HRT for five years or more may be at a heightened risk for breast cancer. However, the heightened risk seems to occur primarily in women using combined (estrogen and progesterone mixture) HRT, as opposed to estrogen-only HRT. However, estrogen-only HRT increases risk of uterine cancer. The elevated breast cancer risk appears to be reversible in that women who discontinued HRT for five or more years show no more increased risk for breast cancer than women who never used it in the first place.

    There are real benefits to HRT that should not be dismissed lightly just because of the elevated breast cancer risk it may come with. Talk to your doctor about your risks and benefits with regard to HRT. HRT may be a good idea for you if you are at a low risk for breast cancer and could benefit from its therapeutic effects. However, if you are already at a high risk for breast cancer you should carefully weigh the risks and benefits before beginning HRT.

  • Obesity and Poor Diet. Research has established a link between being overweight and an elevated risk of postmenopausal breast cancer. This seems to be because the majority of reproductive hormones in postmenopausal women is produced in the fat cells.  Therefore, the more fat cells a woman has the higher their reproductive hormone levels.

    Getting one's self down to a healthy weight and staying there is likely to be a means of reducing one's cancer risk. The best way to combat obesity is to combine a balanced and nutritional diet with a consistent exercise program. Reduced or eliminating portions of foods known to be high in saturated (meat, dairy, etc.) and 'trans fats' (packaged baked goods often contain 'partially hydrogenated' oils which are, in fact, trans fats) may further reduce risk as well. There are numerous benefits to maintaining a healthy body weight besides possibly lowering your cancer risk. Losing weight can also reduce your risk for heart disease and leave you feeling healthier and more energetic.

  • Failing To Exercise. Some recent studies have found a small relationship between moderate exercise and decreased risk of breast cancer. Exercising regularly can help combat obesity as well which further lowers cancer risk. Aerobic exercises, such as swimming, brisk walking, jogging, and playing tennis are best bets as they are easy and enjoyable. However, any activity that will get your heart rate up for an extended period of time will be beneficial. It is a good idea to check with your doctor before beginning any kind of vigorous exercise program.

  • Breast Feeding. Multiple studies have demonstrated that breast feeding is associated with reduced risk of breast cancer. In addition, the longer you breast feed the better the cancer protection you appear to achieve.

  • Excessive Alcohol Intake. Drinking alcohol has been shown to slightly increase the risk of breast cancer. There is a relationship between how much alcohol is consumed and how large breast cancer risk becomes (with women who drink more alcohol being at higher risk for contracting breast cancer than women drinking less alcohol). As alcohol is implicated in numerous health problems, it is best to limit daily alcohol intake to one drink, or to abstain from it altogether.

The more of these risk factors you can eliminate from your life the better your chances may be of avoiding breast cancer.

 




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