Breast Cancer Risk Factors: What You Should Be Aware Of

It is completely understandable if you are worried about your risk of developing breast cancer. Knowing the risk factors can be a helpful way to ease some of those concerns. While we know that the main causes for cancers, including breast cancer, are changes in the DNA of cells, what causes these changes remain largely unknown. What we do know are the main risk factors that may increase or decrease the risk of breast cancer. Some of these factors have been extensively studied, and the research consistently shows their impact on breast cancer risk. Having this knowledge can be an important step towards early detection.

There are two types of risk factors:

• Non-Modifiable Risk Factors

Unfortunately, there are factors beyond our control that increase the risk of breast cancer. In such cases, alternate methods may be explored to overcome these risks.

• Modifiable Risk Factors

Studies have shown that our choices and environment can influence certain factors that are associated with breast cancer. While it is not possible to completely eliminate the risk, making certain changes can still help reduce it to some extent.

The following are the main risk factors associated with breast cancer that cannot be modified:

• Age

As you age, your risk of developing breast cancer increases. It is important to be mindful of your breast health, including practicing breast self-awareness and undergoing breast cancer screening as you grow older. Typically, women around the menopausal age of 50 and older are more likely to be diagnosed with breast cancer. For example, the risk of breast cancer from birth to age 49 is 2.1% (1 in 49 women) compared to 2.4% from age 50–59, 3.5% from age 60–69, 7% for age 70 and older, and 12.9% risk over one’s lifetime.

• Sex

Breast cancer primarily affects females, with males accounting for only 1% of all reported cases.

• Personal history of breast cancer

Individuals who have experienced breast cancer previously are more likely to develop a new breast cancer in either the same or the other breast.

• Genetic risk factors

Individuals with inherited genetic mutations that predispose them to breast cancer are more likely to develop it. Such mutations account for 5-10% of all breast cancer cases. The BRCA genes (BRCA1 and BRCA2) frequently cause hereditary breast cancer, with lifetime breast cancer risk of about 60–80%. There are many other mutations that can result in increased risk of breast cancer. If one knows that they have a genetic mutation that increases cancer risk, one can take steps to prevent the cancer, including risk reduction procedures, or detect it early through breast cancer screening.

• Family history of breast cancer

Individuals with close blood relatives with breast cancer have a higher risk of getting breast cancer. Having a first-degree relative (mother, sister, or daughter) with a history of breast cancer nearly doubles a woman's risk of developing breast cancer. Having two first-degree relatives with a history of breast cancer triples the risk. Individuals with a male first-degree relative (father or brother) who has had breast cancer may also have a higher risk of breast cancer.

• Age at first menstrual period

Having the first menstrual period at a younger age is associated with a higher risk of breast cancer due to the longer period of exposure to estrogen.

• Age at menopause

Reaching menopause at an older age increases the chance of having breast cancer. The later the menopausal age, the more menstrual cycles one goes through, and thus has a slightly higher risk of breast cancer. The increase in risk is likely due to longer lifetime exposure to estrogen.

• Not having children, later age at first pregnancy

Women who give birth at age 20–25 compared to age 30 are at lower risk of developing breast cancer, while women who have a baby at age 35 or later or do not have any children are at similarly higher risk. The protective effect is thought to be due facilitation of breast cell differentiation during pregnancy. This association largely applies to hormone-dependent breast cancer.

• Breast density

Women with dense breasts are at higher risk of breast cancer. While the exact reason is unconfirmed, it could be because dense breasts have more cells that can turn cancerous. Breasts are made up of fatty tissue, fibrous tissue, and glandular tissue. Fibrous and glandular tissues, which are more prevalent in dense breasts, are harder to see through on mammograms, making it harder for radiologists to spot tumors in dense breasts. This may delay diagnosis and treatment.

• Presence of benign breast disease

Having certain benign breast conditions, especially those with proliferative (or quickly-dividing) lesions, may increase breast cancer risk.

• History of radiation therapy

Women who have had radiation treatment to their chest or breasts for other diseases (usually a different cancer type) when they were younger have a higher risk of developing breast cancer. This increased risk is even higher in young women or teenagers who have undergone radiation when their breasts were still developing. The dose of radiation also affects the increase in risk. More frequent and intense breast cancer screening is recommended for these patients.

• Race and ethnicity (studies in the United States only)

In studies done in the United States, White / Caucasian women are slightly more likely to develop breast cancer compared to women who identify as Black / African American, though some of the difference can be explained by lifestyle factors. Asian and Hispanic women have a lower risk of developing breast cancer. Black and Hispanic women are more likely to develop breast cancer at a younger age compared to White / Caucasian women.

Here are the main factors associated with a higher risk of breast cancer that are may be modified through behavior or lifestyle changes:

• Alcohol consumption

Drinking alcohol increases the risk of developing breast cancer by approximately 5–15%, with higher amounts of alcohol associated with a greater risk of cancer.

• Smoking

A history of smoking increased the risk of developing breast cancer risk by about 10%.

• Overweight / high body mass index (BMI)

Obesity increases the risk of breast cancer in postmenopausal women. This is likely due to the fact that fat tissues make estrogen, with a higher exposure of estrogen in women whose ovaries no longer make it likely resulting in higher cancer risk. Weight loss in overweight post-menopausal women decreases the risk of developing breast cancer by 12%–57% depending on the amount of weight loss and study.

Interestingly, high BMI is associated with a lower cancer risk in pre-menopausal women.

• Physical activity

Women who regularly exercise have a lower risk of breast cancer. In observational studies, physical activity decreases the risk of breast cancer by 11–22%.

• Breastfeeding (not modifiable in some cases)

Breastfeeding reduces the risk of breast cancer. In one large research study, it was estimated that each year of breastfeeding reduces the relative risk developing breast cancer by 4.3%.

• Birth control

Though some studies have not found an association between hormone-containing contraception use and breast cancer, others found that the use of combination estrogen-progesterone oral contraceptives (OCP) increases breast cancer risk by 20–30%. The absolute risk is still low since most women who use OCPs are young and decreases back down to zero in the 2–10 years following discontinuation of OCP use.

• Hormone replacement therapy following menopause.

For some women, symptoms of menopause, including hot flashes, difficulty sleeping, mood changes, weight gain, joint stiffness, and others are difficult to tolerate. Combined oral estrogen-progesterone use after menopause has been associated with a 20%–25% increase in the risk of developing breast cancer. However, absolute risk level for women ages 50-59 taking combined hormone replacement therapy for 5 years is fairly low, resulting in an extra 2.5 new cases of cancer per 1000 women. Unopposed estrogen replacement in women who have had a hysterectomy has not been associated with an increased breast cancer risk.

It is helpful to understand the risk factors of breast cancer, but it is important not to overanalyze them without consulting a medical professional. Having a high risk does not necessarily mean an individual will develop breast cancer. If you have concerns, it is advisable to speak with a doctor who can provide an accurate evaluation and guide you on the next appropriate steps to take. Your health and well-being matter, so remember to prioritize taking care of yourself.