1 in 8 Women will be diagnosed with breast cancer during her lifetime: Understanding risk factors for breast cancer
While there is no single method to prevent breast cancer, there are steps we can take to reduce the risk. Risk factors are characteristics that may increase the likelihood of developing breast cancer, but they are not harmful on their own. Even women with multiple risk factors often have a low overall risk, with around 85 percent of breast cancer cases occurring in women without significant risk factors.
It's essential to understand that some risk factors are modifiable – meaning we can change them – while others are non-modifiable and beyond our control.
Gender and Age
Two of the most significant breast cancer risk factors, over which we have no control, are:
- Being a woman
- Getting older
Gender:
Being born a biological female is the main risk factor in being diagnosed with breast cancer. While men may develop breast cancer, the disease is more prevalent in the female population.
Age:
As we age, the chance of developing cancer rises. Most cancer diagnoses happen after the age of 55 with the median age at breast cancer diagnosis being 63.
The National Cancer Institute’s (Cancer.gov, 2020) recent SEER Cancer Statistics Review reports estimate a lifetime risk of breast cancer at approximately 1 in 8 for women. While this number may seem high, it’s important to remember that this risk is spread over a woman’s entire lifetime. Breast cancer is much more common in older women, so the risk varies significantly by age. Looking at breast cancer risk by decade of life can make these statistics more meaningful and easier to understand.
Here is the 10-year risk for breast cancer by decade:
- Age 30 . . . . . . 0.49% (or 1 in 204)
- Age 40 . . . . . . 1.55% (or 1 in 65)
- Age 50 . . . . . . 2.40% (or 1 in 42)
- Age 60 . . . . . . 3.54% (or 1 in 28)
- Age 70 . . . . . . 4.09% (or 1 in 24)
Personal History of Breast Cancer or Other Cancer
The third most significant risk factor is having a personal history of breast cancer.
“Women who have been diagnosed with breast cancer are 3-4 times more likely to develop a new cancer in the other breast or a different part of the same breast.” (Breastcancer.org, 2024)
Specifically, a diagnosis of a typical ductal or lobular hyperplasia after biopsy may increase the risk of developing invasive breast cancer. Women who have been diagnosed with other cancers, such as colon, ovarian, or endometrial may be at an increased risk.
Personal History of Fibrocystic Changes
Fibrocystic changes do not significantly increase a woman's risk of developing breast cancer since most women have some aspect of this condition. Only abnormal changes in the cells lining the breast duct are associated with increased breast cancer risk. This diagnosis can only be made through a biopsy.
Breast density, as evaluated by a mammogram, can also increase your chances of breast cancer. Having denser than average breasts can also make detecting breast cancer more difficult. It’s important to note - breasts that feel dense by touch have not been correlated with an increased breast cancer risk.
Knowledge is key, speak with your primary care provider or OB/GYN and discuss what additional screening measures can be taken for dense breasts. This will often include routine ultrasounds in addition to mammograms.
Family History
A history of breast cancer in immediate female relatives (mothers, daughters, and sisters), especially at an early age, may indicate a genetic predisposition and constitutes a major risk factor in five to 10 percent of breast cancer patients. Both maternal and paternal sides of the family should be considered when looking at family history. The risk seems to increase when cancer has appeared in both breasts of relatives.
Not all family history of breast cancer increases the risk. The risk increases when a first-degree relative (sister or mother) has developed breast cancer at an early age, particularly in their 30s before menopause, or when multiple family members have breast cancer.
However, 85% to 90% of all breast cancers are diagnosed in women with no family history. Breast cancer risk is individual and based on the interaction between a woman's environment and heredity.
Weight
Overweight and obese women have a higher risk of being diagnosed with breast cancer. This risk is further increased after menopause. This, however, is a modifiable risk factor, meaning this risk factor can be decreased by improving diet, including balanced meals rich in fruits and vegetables.
A study published in Nature Communications (July 21, 2023) found breast cancer cells have more inflammation and different mutations in women with a body mass index (BMI) of 30 or higher.
Diets high in animal products may contribute to an increase in breast cancer in contrast to plant-based diets. The Mediterranean Diet is recommended to reduce weight and enable nutrition to promote a healthier lifestyle. This way of eating limits refined carbs and red meats, and focuses on healthy grains, fruits, vegetables, lean meats, and fish.
Foods high in refined carbs and sugar are known to increase insulin levels in the body. Research shows that increased insulin sensitivity can promote breast cancer cell growth.
Exercise
Getting regular aerobic exercise and strength training for as little as 30 minutes a day can reduce your risk for breast cancer.
In addition to reducing cancer risk, maintaining an active lifestyle reduces your risk for heart disease, diabetes, stroke, and osteoporosis for which women after menopause are already at an increased risk.
Pregnancy and Breastfeeding History
Did you know breast cells are made in adolescence? They are considered immature and highly active until your first full-term pregnancy.
“Breast cells become mature and will grow in a more regular way and be less responsive to hormonal changes than the immature cells…Women who haven't had a full-term pregnancy or have their first child after age 30 have a higher risk of breast cancer compared to women who gave birth before age 30” (BreastCancer.org, 2023)
According to a 2023 study published in Cancer Med., breastfeeding reduces the risk of breast cancer by 4.3% for every 12 months of breastfeeding, which is in addition to the 7% decrease in risk observed for each birth. Breastfeeding has been shown to primarily reduce the risk of triple‐negative breast cancer (20%) as well as in carriers of BRCA1 mutations (22–50%).
Women with a family history of breast cancer should particularly consider breastfeeding as a way of reducing their cancer risk.
Alcohol and Smoking
Research shows that greater alcohol consumption is linked to higher breast cancer risk. However, any amount of alcohol is associated with an increased risk of breast cancer
Avoiding alcohol is ideal, but if you do choose to consume it:
- Limit yourself to no more than 7 servings per week.
- Make sure you are getting at least 400 micrograms of folate a day through diet, supplementation (folic acid is the supplement form), or both. Getting enough folate appears to lower the increased risk from alcohol.
If you currently smoke, reach out to your care provider to guide you to successful strategies for smoking cessation. Do not be afraid to ask for help, there are pharmacological and nonpharmacological options to help you quit. Ask your primary care provider to learn more about these resources.
Evaluate Hormone Use
Knowing the risks of hormone replacement therapy and hormonal birth control is a crucial step to understanding how these medications can affect your risk for breast cancer. Discuss with your OB/GYN on if the benefits for you outweigh the risks.
Supplements & Breast Cancer
Many studies have identified a link between low vitamin D levels and the production and progression of breast cancer. The exact reason for this is unknown, however many newly diagnosed breast cancer patients are found to have low vitamin D levels.
Vitamin D:
- Helps the body absorb calcium – optimizing bone health.
- Slows tumor growth, according to research.
Reducing Risk & Imaging Surveillance
Although some risk factors cannot be modified, we can take steps to reduce the number of risks we have – like:
- Managing weight
- Eating healthily
- Exercising
Screening mammograms are essential. Starting at age 40, it is important to make sure you are getting a yearly mammogram. Screenings can detect breast cancer in patients who do not have any symptoms.
Breast cancer screening cannot prevent breast cancer from developing, but it can help detect it earlier, when it is easier to treat. Breast cancers found during screening exams are more likely to be smaller and less likely to have spread outside the breast - making cancer easier to treat.
Ask your gynecologist or primary care doctor about a tailored screening program. This may include additional, or several types of imaging tests based on your needs and individual risks.
Disclaimer: While I am a doctor, I am not your doctor. The content in this blog is for informational and educational purposes only and should not serve as medical advice, consultation, or diagnosis. If you have a medical concern, please consult your healthcare provider, or seek immediate medical treatment.
References
- “Breast Cancer Risk Factors.” Breastcancer.Org - Breast Cancer Information and Support, Breastcancer.org, 19 July 2024, www.breastcancer.org/risk/risk-factors.
- “Breast Cancer Risk in American Women.” NCI, 2020, www.cancer.gov/types/breast/risk-fact-sheet.
- “Pregnancy History.” Breastcancer.Org - Breast Cancer Information and Support, Breastcancer.org, 4 Jan. 2023, www.breastcancer.org/risk/risk-factors/pregnancy-history.
- Stordal B. Breastfeeding reduces the risk of breast cancer: A call for action in high-income countries with low rates of breastfeeding. Cancer Med. 2023 Feb;12(4):4616-4625. doi: 10.1002/cam4.5288. Epub 2022 Sep 26. PMID: 36164270; PMCID: PMC9972148.
