Breast cancer risk factors. That’s the subject of our podcast today.
Surreal. Few words have a greater impact. Many describe the time around hearing “You have breast cancer” as surreal, with many individuals moving from confusion to shock and grief, anger, fear, and despair. Most need time to work through these emotions. Once you do, you should be better able to navigate the journey to becoming better.
Breast cancer is a story with many chapters. No matter where you find yourself in the journey, I designed this podcast to help you navigate it. Herein, you will find information about why you may have gotten breast cancer (and basic, sustainable lifestyle adjustments that might improve the odds of it never coming back), what it looks like under the microscope, staging (extent of cancer), prognosis, and cancer management. For brevity, I will not address natural medicine approaches, nor focus on psychological well-being in this book. I do hope to be a source of knowledge and support for you.
Breast cancer is the most common non-skin cancer among women worldwide. In 2021, an estimated 281,550 new cases of invasive breast cancer were diagnosed in women in the U.S., along with 49,290 new cases of non-invasive (in situ) breast cancer. Worldwide, there are over 2 million new cases each year.
From the 1940s until the 1980s, breast cancer incidence (new cases) rates in the USA increased slightly. In the 1980s, incidence rose greatly (likely due to increased mammogram-based screening) and then leveled off during the 1990s. The incidence of breast cancer declined in the early 2000s. This decline appears to be linked to a drop in the use of menopausal hormone therapy (after the Women’s Health Initiative study showed its use increased breast cancer risk). Since 2007, the incidence of breast cancer has remained roughly stable.
Risk
While we cannot say with certainty why you (or someone about whom you care) got breast cancer, the disease is linked to many risk factors. We will review these in this chapter, but first I want to introduce some key definitions:
• Absolute risk
Odds you will develop a specific disease over a certain time
• Lifetime risk
Odds you will develop a disease in your lifetime
• Risk factors
Anything affecting your risk of getting a particular disease
• Relative risk
The ratio of absolute risks
We will also look at factors that are associated with a lower risk of getting breast cancer. We sometimes refer to such factors as protective risk factors or just protective factors.
Age
Age is a risk factor for breast cancer among both women and men. The older you are, the more likely you are to get breast cancer. Less than five percent of women diagnosed with breast cancer in the USA are younger than 40. About half of women with breast cancer will be diagnosed after age 60. While the incidence of breast cancers driven by estrogen increases with age, the incidence of estrogen receptor-negative breast cancer increases until age 50, then levels off.
Female
Being a female is a strong risk factor for breast cancer. While men can get the breast cancer, the disease is approximately 100 times more common among women. However, the male incidence has risen slightly since 1975 (from 1 to 1.3 per 100,000). Men are more likely than women to be found with advanced-stage breast cancer, likely the result of lower awareness, and the lack of screening among men.
Personal history of breast cancer
A personal history of ductal carcinoma in situ (DCIS) or invasive breast cancer increases the risk of an invasive cancer in the opposite breast. This risk may be on the order of 0.5% per year, but the risk varies by factors such as your age at initial diagnosis, whether you have a so-called breast cancer gene (BRCA), and by the primary cancer hormone receptor status.
Height
The taller you are, the bigger your risk of getting breast cancer. In a study of over 100,000 women (followed for twelve years), women 5 feet 7 inches (1.75 meters) or taller were 1.6-times more likely to get breast cancer than women under 5 feet 2 inches (1.6 meters). Every 2 inches (5 centimeters) added 11 percent risk, or increased risk by a factor of 1.1.
Density
Breast density describes the proportions of different breast tissue types. High breast density means there is a greater amount of breast and connective tissue, as compared to breast fat.
Low breast density means that there is a greater proportion of fat. In 2006, a meta-analysis (study of studies) showed breast density to be an independent risk factor for breast cancer. Women with very high breast density may be up to four to five times more likely to get breast cancer, compared to women with low breast density.
Many, but not all research studies demonstrate a link between breast density and the risk of getting breast cancer. Still, many states in the USA have enacted legislation mandating the reporting of breast density to women who have undergone mammography.
Geography
Breast cancer incidence rates around the world vary greatly. Developed countries (such as the United States, England and Australia) have higher rates than do developing countries (such as Cambodia, Nepal and Rwanda). Within the United States, incidence also varies (here are 2018 data):
• Higher
Hawaii, Montana, Rhode Island, New Hampshire, District of Columbia, North Carolina, Delaware, New Jersey, Nebraska, Connecticut
• Lower
New Mexico, Arizona, Texas, Wyoming, Utah, Florida, Alabama, West Virginia, California, Missouri
Worldwide, breast cancer incidence is highest in Belgium, followed by Luxembourg, the Netherlands, France, New Caledonia (France), Lebanon, Australia, the United Kingdom, Italy, and New Zealand.
Mortality also varies by geography. While variations in mortality rates reflect variations in incidence, the other major contributor to the mortality rate is survival. Breast cancer mortality rates among white women tend to be highest in the North Central, Mid-Atlantic, and Western USA. Among black women, the highest death rates are found in some of the South Central and Mid-Atlantic states, as well as California.
Some factors that may contribute to these differences include variations in risk factors, access to screening, and treatment. These are in turn influenced by socioeconomic factors, legislative policies, and proximity to medical services.
Race
Among women in the USA, breast cancer incidence and mortality vary by race and ethnicity. Non-hispanic whites have the highest risk, followed by African-Americans*, then Asian and Pacific Islanders. American Indian and Alaska natives have the lowest incidences . Here are the numbers from the Komen Foundation (www.komen.org/)
Race and ethnicity Lifetime risk of breast cancer
White 13%
Black 12%
Asian and Pacific Islander 11%
Hispanic 11%
American Indian or Alaska Native 8%
African-American women have the highest breast cancer-related death rate, while Asian-American and Pacific Islander women have the lowest. Between 2008 to 2012, rates of breast cancer diagnosis increased by 0.4 percent per year in African-American women, compared to 1.5 percent per year among women identifying as Asian or Pacific Islanders. The rates of diagnosis in the time period remained stable among women of white, Hispanic, American Indian and Alaska Native origins.
American Cancer Society researchers analyzed data from the National Cancer Institute’s Surveillance, Epidemiology and End Results, and found that in 2012 black and white women were diagnosed with breast cancer at about the same rate.
In seven states, the rates of breast cancer among black women surpassed the rates of white women between 2009 and 2012. That increase was seen primarily in the Southern region of the country: Alabama, Kentucky, Louisiana, Mississippi, Missouri, Oklahoma and Tennessee.
__________
*Among women under 45, African-American incidence is the highest.
Family
Most women with breast cancer do not have a family history of the disease. In fact, only about 13 percent have a first-degree relative (mother, sister or daughter) with breast cancer. However, a family history of certain cancers (for example breast, ovarian, or prostate cancer) can increase your risk of breast cancer.
• A first-degree relative (sister, mother, or daughter) has breast cancer: Your breast cancer risk may double.
• Two first-degree relatives have breast cancer: Your risk may triple.
Inheritedgenetics
Only 5 to 10 percent of all breast cancers are directly linked to the inheritance of known breast cancer susceptibility genes such as BRCA1, BRCA2, p53, ATM, and PTEN. Breast and ovarian cancer appear to be more common among women of Ashkenazi (with ancestors from Central or Eastern Europe) Jewish descent, given a higher prevalence of risk-raising BRCA1 and BRCA2 (BReast CAncer genes 1 and 2) mutations.
Everyone has BRCA1 and BRCA2 genes. Some have an inherited mutation in one or both of these genes that increases the risk of several cancer. One in 40 women of Ashkenazi Jewish descent carry one of these mutations, compared to one in 400 in the general population. Of those with breast cancer, roughly 10 percent will have a BRCA mutation. Among women with breast cancer in the non-Ashkenazi Jewish population, about five percent carry a BRCA mutation.
Are BRCA mutations limited to individuals of Askenazi Jewish descent? Clearly, the answer is no; various ethnic and racial groups are susceptible as well. For example, young African-American women with a breast cancer diagnosis at age 50 years or younger have a much higher BRCA mutation frequency than that previously reported among young white women with breast cancer, according to a recent United States-based study.
Women who have inherited mutations in the BRCA1 or BRCA2 genes are significantly more likely to develop breast or ovarian cancer, especially at a younger age. About 5% of women with breast cancer in the United States have mutations in a BRCA1 or BRCA2 gene, based on estimates among non-Hispanic white women. Having a BRCA gene mutation can raise your risk of several cancer types, including melanoma, as well as ovarian, breast (including among males), and prostate cancer.
To learn more, check out my book on breast cancer:
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