Breast Cancer Risks, Prevention & Screening

0 Posted by - October 4, 2013 - PREVENTION

October is National Breast Cancer Awareness Month and an excellent opportunity to think about your breast cancer risk, prevention and screening strategies.   With the exception of skin cancers, breast cancer is the most common form of cancer among women in the United States.  The average US woman’s lifetime risk of developing invasive breast cancer is 12%.   The American Cancer Society estimates that in 2013 there were over 232,000 women newly diagnosed with invasive breast cancer and over 2.8 million survivors living in America.  The good news is that breast cancer incidence rates have been decreasing since 2000, due in part to decreased use of hormone replacement therapy (HRT) and early detection.

Gender, Age & Genes

While we still do not fully understand the exact mechanism of breast cancer, several risk factors have been proven to increase a person’s chances of developing breast cancer.   The most significant risk factors are being a women and increasing age, clearly factors we cannot control.  Another risk factor that has recently made headlines is inheriting mutations of the BRCA1 or BRCA2 genes.  Approximately, five to ten percent of breast cancers can be linked to gene mutations, with mutations of the BRCA1 and BRCA2 genes being the most common.   In February of this year, Angelina Jolie underwent a widely publicized prophylactic double mastectomy after she discovered she had a mutation of BRCA1 and her personal breast cancer risk was 87%.  Jolie’s mother passed away from ovarian cancer at the age of 56, which prompted Jolie to undergo genetic testing.   Women with a BRCA1 mutation generally have a 55-65% risk of developing breast cancer before age 70, and often at a younger age than other women.  For women with a mutation of the BRCA2 gene, the risk is 45%.   Together, theses mutations account for approximately 15% of all ovarian cancers.

Reproductive Risk Factors & Hormone Replacement Therapy

So, what risk factors can you control?   Many of the risk factors are related to our hormones and exposure to hormone levels in our bodies.   Pregnancy has a protective effect against breast cancer.  Women who have there first child before age 20 and women who have more than one child have a lower risk of developing breast cancer.  Women who have their first child after age 30 or do not have children have a slightly higher risk.   Breastfeeding for over one year or longer has also been linked to lowering your risk.

Hormone replacement therapy (HRT) with combined estrogen and progesterone to treat the symptoms of menopause has been shown to increase a woman’s risk of developing breast cancer.  In 2002, researchers stopped the NIH Women’s Health Initiative study early due to the findings that the use of combined estrogen and progesterone increased breast cancer risk.  They also found that women on combined hormone therapy were being diagnosed with more aggressive forms of breast cancer, likely due to the fact that combined hormone replacement therapy increases breast density making detection with mammograms more difficult.  Over the last decade, the use of hormone therapy has markedly decreased but questions still remain.   A recently published post intervention follow up study, supports the initial findings.  The researchers again concluded that the risk outweigh the benefits (1).  Each year a woman takes hormones replacement therapy, her risk of breast cancer increases, with the risk returning to normal within 3 to 5 years of discontinuing use.  If you are taking hormone replacement therapy, discuss its effects with your health care provider and use it for as short duration as possible.

Risk Factors You Can Prevent With a Healthy Lifestyle

A healthy lifestyle has a protective effect. Maintaining a healthy weight and limiting alcohol consumption can also help keep your breasts healthy.   A recent study in the Journal of the National Cancer Institute found that alcohol consumption between a woman’s first period and her first pregnancy has a significant effect on breast cancer risk.  Breast tissue is particularly sensitive to carcinogen exposure prior to first pregnancy and thus alcohol consumption at a younger age increases risk of developing cancer later in life.    The authors found a stronger association between alcohol consumption and the risk of breast cancer when the timeframe between first period and first pregnancy was longer.    The risk from alcohol was also found to be dose-dependent, meaning that the more alcohol a woman drinks in her teens and before her first pregnancy, the more the risk increases. (2)

Eating well and maintaining a normal weight can also help prevent breast cancer.  Obesity is a risk factor for the development of several cancers including breast, endometrial, kidney, colon, and esophageal.  Obesity is also an important prognostic factor for how well people who are diagnosed with breast cancer respond to treatment.   A study in the Journal of Clinical Oncology, found that obesity was associated with a later breast cancer diagnosis and thus more advanced disease, an increased development of distant metastases and an increased risk of death after the diagnosis of cancer.  The authors found a 38% increased risk of death in obese patients compared to normal weight women after the diagnosis of breast cancer. (3)


Discuss your personal and family history with your primary care physician and ask them to calculate your personal risk for invasive breast cancer using the National Cancer Institute’s Breast Cancer Risk Assessment Tool.

Women with an average risk of breast cancer should have a physician perform a clinical breast exam every 1 to 3 years beginning at age 20.   At age 40, women should begin having annual screening mammograms.

It is also essential to know your own body and see your physician if you develop any concerning signs, such as a lump or hard knot with your breast or underarm; swelling, redness or warmth of the breast; change in breast size or shape; dimpling or puckering of the skin; itchy, scaly skin or rash on the nipple; pulling in of your nipple or other parts of the breast; nipple discharge that starts suddenly; new pain in one spot that doesn’t go away.

To find a low cost screening location in Colorado or near you, go to the CDC’s National Breast and Cervical Cancer Early Detection Program (NBCCEDP) at

Non-Modifiable Risk Factors

Increases Risk


Ninety-nine percent of cases occur in women


Risk increases with age


White women have slightly higher risk;

Asian, Hispanic, and Native-American women have a lower risk

Family History

Risk approximately doubles if a first-degree relative (mother, sister, daughter) has breast cancer. About 15% of women who get breast cancer have a family history of it.


Together, BRCA1 and BRCA2 mutations account for about 20- 25% of hereditary breast cancers and about 5-10% of all breast cancers. 

Personal History

History of breast cancer, lobular carcinoma in situ or certain other benign breast conditions increases risk

Number of Menstrual Cycles

First menstrual cycle before age 12 or menopause after age 55 increases risk

Exposure Risk

Exposure to breast radiation at a young age or expose to DES during pregnancy increases risk

Dense Breast Tissue

Increased risk, also can make diagnosis with mammograms more difficult



Modifiable Risk

Lowers Risk

Alcohol Consumption

Decreased alcohol consumption between age of first menstrual cycle to first pregnancy lowers risk


Being a normal weight after menopause decreases risk; being overweight or obese after menopause increases risk


Use of Depo-Provera birth control or combined estrogen-progesterone hormone replacement after menopause are both associated with increased risk.  Risk returns to normal over time when medications are discontinued.


First pregnancy before age 30 lowers risk.  Multiple pregnancies and first pregnancy at a younger age lowers risk.


Breastfeeding slightly lowers risk, particularly breastfeeding over 1year.


1. Manson, J, Chlebowski, R, Stefanick, M et al. Menopausal Hormone Therapy and Health Outcomes During the Intervention and Extended Poststopping Phases of the Women’s Health Initiative Randomized Trials. JAMA. 2013;310(13):1353-1368. doi:10.1001/jama.2013.278040.

2 Ying, L, Colditz, G, Rosner, B et al.  Alcohol Intake Between Menarche and First Pregnancy: A Prospective Study of Breast Cancer Risk. JNCI J Natl Cancer Inst (2013) doi: 10.1093/jnci/djt213

3. Ewertz M, Jensen M-B, Gunnarsdóttir KA, et al. (2011) Effect of obesity on prognosis after early-stage breast cancer. J Clin Oncol 29:25–31.



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