Causes and Risk Factors of Breast Cancer

Healthcare providers seldom know why one woman develops breast cancer and another does not. No one knows the cause of breast cancer.

Still, breast cancer is one of the most well-researched cancers in the world, and the flood of research gives us hope that the causes will soon be found.

What we do know are the many risk factors and potential causes of breast cancer. To understand breast cancer we must start with the fact that all breast cancer develops from damaged DNA. Race-specific DNA mutations and differences in tumor biology are prime areas of insight in the quest to cure breast cancer. 

In looking into the causes of breast cancer, researchers also hope to understand why Black women younger than 35 years old get breast cancer at two times the rate of White women and die from breast cancer three times as often as White women.

This article looks into the potential causes and risk factors for breast cancer, with insights into the effect on Black women.

Common Causes

Most breast cancers are carcinomas, which means that the cancer cells are derived from epithelial cells that line the milk ducts or glands of the breast. Some breast cancers can also develop in the lobes and stroma of the breast.

Changes in the DNA of a woman’s breast begin in the 12 to 20 sections of tissue, called lobes, which surround the nipple like petals on a flower. Each lobe contains several glands, where milk is produced.

The glands are connected by ducts that transport the milk to the nipple. The cells that make up ducts are epithelial cells, and this is where breast cancer starts after changes in the DNA allow abnormal cells to grow.

Breast cancer may be related to DNA changes (mutations, amplifications, etc), but this is not always the case.

Effect on Black Women

Breast cancer rates in Black women have increased more rapidly—0.9% per year compared to 0.4% in White women—equalizing breast cancer rates in both groups. The main reason for this is the massive success of breast cancer awareness campaigns.

More Black women are getting tested, so naturally, more breast cancers are being detected. Still, the rise in breast cancer diagnoses is alarming.

Genetics

Genetic damage to your DNA is very often found in breast cancer, but why or how this happens is a mystery. Some genetic mutations are passed down in families—about 5% to 10% of breast cancers are caused by abnormal genes passed from parent to child—while others are spontaneous.

Up to 25% of hereditary cases are due to a mutation in one of a few rare genes:

• BRCA1
• BRCA2
• PTEN
• TP53
• CDH1
• STK11

These confer up to an 80% lifetime risk of breast cancer. An additional 2% to 3% of cases are due to a mutation in one of the following rare, less penetrating genes:

• CHEK2
• BRIP1
• ATM
• PALB

These are each associated with a twofold increase in the risk of developing breast cancer.

Everyone has BRCA1 and BRCA2 genes that help to repair cell damage and keep breast cells growing normally. When these cells do not function properly, they allow mutated DNA to create abnormal proteins in cells. These mutations may be passed on from generation to generation, and breast cells remain damaged, increasing breast cancer risk. 

The breast cancer risk for Black women with a BRCA1 or BRCA2 genetic mutation is as follows:

• 69% to 72% lifetime risk of developing breast cancer
• Increased lifetime risk of developing other cancers such as ovarian cancer
• Higher-than-average risk of recurrent breast cancer or developing a new, second breast cancer after an initial diagnosis

Research shows that about 5% of women diagnosed with breast cancer in the United States have an abnormal BRCA1 or BRCA2 gene, but this is likely a gross underestimation as the data captures mostly non-Hispanic White women.

Identifying genes that cause breast cancer has led to a rise in personalized medicine, a new age method of personalizing a treatment plan by targeting problem genes.

Gene expression tests are used to learn more about cancer and tailor treatment. A biopsy is performed, and tests look at the patterns of a number of different genes, a process called gene expression profiling.

The patterns found can provide clues that help oncologists predict if certain early-stage breast cancers are likely to come back after initial treatment. They can also help healthcare providers identify certain chemotherapy treatments that will be most effective after breast surgery.

Lifestyle Risk Factors

No one knows the cause of breast cancer, but there are known risk factors such as:

• Genetic mutations (most notably BRCA1 and BRCA2 mutations)
• Family history of breast cancer
• Reproductive history: A history of early periods (before 12 years old) or late menopause (after age 55) have been associated with a higher risk of developing breast cancer.
• More dense breasts: Breasts with higher amounts of connective tissue vs. fat can mask cancers. 
• Personal history of cancer
• Prior exposure to radiation: Young women who have had radiation therapy for another condition, like Hodgkin lymphoma, are especially at high risk.
• Taking hormones: Taking some forms of hormone replacement therapy for five or more years has been associated with a higher risk of breast cancer.
• Women who took the drug diethylstilbestrol (DES), which was given to some pregnant women in the United States between 1940 and 1971 to prevent miscarriage, have a higher risk. 
• Smoking
• Heavy alcohol use
• Obesity: Living with overweight or obesity is particularly problematic after menopause. 
• Sedentary lifestyle

Some factors like smoking, obesity, and alcohol use are preventable factors, while others like older age, reproductive history, and your genetics are out of your control.

More research is being done to highlight the many ways you can limit your cancer risk. One area of particular interest is stricter regulation of the ingredients used in cosmetic products.

Some research has even pointed to targeted marketing of cosmetics as one reason for the significant rise in cancer rates among Black women. While more research needs to be done, some scientists believe that the cosmetic products that are often marketed to Black women contain endocrine disruptors—such as hydroquinone, diethyl phthalate (DEP), and even mercury—that may put you at higher risk for cancer.

Access to Care

Black women are dying from breast cancer at an alarming rate. The following conclusions from the American Cancer Society’s Breast Cancer Facts & Figures 2019–2020 may provide some insight on the crisis at hand:

• Black women are not translating breast health awareness into tangible actions. A recent survey found that 92% of Black women believe that breast health is important, but only 25% say that they have recently discussed breast health with their family, friends, or colleagues. Further, only 17% have taken steps to understand their risk for breast cancer.
• Black women are more likely to present with advanced-stage cancer upon detection.
• Black women are less likely to have health insurance and therefore are more likely to skip or neglect mammograms. 
• Lack of insurance leads to a lack of access to care. Getting a mammogram without insurance is expensive, and more providers need to provide low-cost options. The true cure to solving access to care issues is to eliminate the racial wealth gap, but that is a long way away. This leaves Black women struggling to pay or stressing over the cost of healthcare services like mammograms and lab work. Not surprisingly, some Black women may not follow-up on abnormal mammogram results because they can’t afford the diagnostic testing, to avoid bad news, or both.
• Black women often go to lower-quality healthcare facilities and receive lower-quality care, so they don’t get the same prompt high-quality treatment that White women receive.
• Black women are nearly three times more likely than White women to get triple-negative breast cancer, a rare and aggressive subtype that is often fatal due to its treatment-resistant nature. It is the only breast cancer subtype that does not have a therapy to prevent a recurrence.
• Younger Black women sometimes get diagnosed at later stages and are more likely to get a diagnosis of triple-negative breast cancer when they do.

Some healthcare providers may be hesitant to address breast cancer with Black people when they come in with other conditions.

Health disparities are so pervasive that it may seem as if there are too many conditions to discuss. Remember that you are entitled to information regarding your overall health, not just the condition that brought you in. Open and honest dialogue with your healthcare provider will make it easier to have the discussions you need.

According to a recent study, the three most commonly reported barriers to mammography were fear of cost, fear of mammogram-associated pain, and fear of getting bad news. Systemic problems such as lack of insurance, concerns over the ability to pay, no primary care physician, and biased physician care add another level of difficulty to an already tenuous situation.

Some factors associated with lower mammogram completion rates include:

• Age lower than 60 
• Health plan membership less than five years
• Family income less than $40,000 per year
• Obesity: Women with obesity were more likely than women without obesity to report “too much pain” from mammograms.
• Recent immigration
• Rural residency

No Black woman should go without a mammogram, whether there are concerns about pain, bad news, or cost. Going to an appointment with a friend may ease your fears, and many providers will work with you to offset the cost of your mammogram. 

More than 30% of Black women do not get their recommended mammograms. More needs to be done to meet this group where they are. Patient reminders via mail and social media, as well as telephone reminders using live callers or automated calls, are excellent ways to raise screening rates. Ask your healthcare professional to provide these services for you if they haven’t already. 

A Word From Verywell

A common misconception that some women hold is that only women with a family history of breast cancer are at high risk of having breast cancer. While these women may be at the highest risk, all women are at high risk.

Lifestyle modifications are a great way to improve your overall health, but for many women, prevention and early detection are just as important to living a happy and healthy life. Screening mammography can detect breast cancer at an early stage when treatment is usually less extensive and more likely to be successful.

If you suspect that you have breast cancer or have any questions regarding breast health, contact a healthcare provider as soon as possible to get some peace of mind. Research shows that early detection is associated with a good prognosis, and many women go on to live cancer-free lives.