Breast Cancer: Risk Factors
Breast Health Guide
|Breast Cancer Risk Factors
Breast cancer affects more than 180,000 American women a year, killing about 40,000 of them. Like all cancers, there is no known cause for breast cancer, it is considered multifactorial, i.e. has many causes (see cancer causes). However there are certain risk factors which may make it more likely for a woman to develop breast cancer. In fact for the princely sum of about $6000 you can order a cancer risk analysis complete with genetic testing which can estimate your chances of developing any cancer. These tests are controversial; while some doctors feel they are worthwhile others think they cause people unnecessary worry. There may be a burden associated with knowledge. The risk factors associated with breast cancer are varied. A risk factor is something that increases the chances of developing a disease. But even then risk factors are not absolute. Most women have some of the breast cancer risk factors but never develop the disease. Even when a woman with risk factors develops breast cancer it is difficult to say just how much those factors contributed to causing the cancer.
There are 3 different types of risk factors associated with breast cancer:
Simply being a woman is a risk factor for breast cancer. Men can develop breast cancer too, but it is 100 times more common in women. Not only do women have more breast cells than men, they are constantly exposed to the growth effects of female hormones estrogen and progesterone. Not sure what the signs are? See breast cancer symptoms for more information.
Many women mistakenly believe that their risk of 'women's cancers' decline after their childbearing years. In fact, the opposite is true. Age is the most important risk factor of all for cancer, including breast cancer. Nearly 50 percent of all cancers occur in people over the age of 65. This is why continual screening is important. For example fewer women over 65 have regular pap smear tests, which means this group are often diagnosed with cervix cancer at a later stage. About 1 in 8 every cases of breast cancer in women younger than 45 are invasive, while this rises to 2 out of 3 in women over 55. See diagnosis of breast cancer to read more about how it is diagnosed.
You are more likely to develop breast cancer if your mother, sister or daughter has been diagnosed with the disease (particularly if they were diagnosed before the age of 50). Between 5 to 10 percent of breast cancer cases are thought to be hereditary, resulting from genetic mutations (defects) inherited from a parent. BRCA1 and BRCA2 are the two primary mutated genes which have been linked to breast cancer. If a woman inherits either of these genes, and this can be confirmed by a genetic test for breast cancer, her genes must still undergo further mutation during life before cancer occurs. Sometimes these further mutations never happen. However simply being born with the mutation means a woman has taken her first step towards breast cancer (as well as ovarian cancer). In America the BRCA mutated genes are most often found in Jewish women of Eastern European origin (Ashkenazi), but they can occur in any ethnic or racial group. Other genetic mutations have been linked to breast cancer, but they do not have as great a role as the BRCAs. These are: ATM, p53, CHEK2, PTEN and CDH1.
A woman who has already had cancer in one breast is 3 to 4 times more likely to develop cancer in the other breast. A regular breast self-examination and mammogram is particularly important in this risk category. Women who have had lumpectomy for a tumor will also need to be monitored carefully.
Ethnicity & Race
African-American women are slightly less like to develop breast cancer than White women, although they are more likely to die from the cancer if they get it. This may partly be explained by the fact that African-American women tend to develop more aggressive tumors. Current statistics show that a white baby girl born in America today has an 11 percent chance of developing breast cancer some time before her 85th birthday. Although 11 percent may sound very high, this is partly due to the fact that women are living longer. Ironically if more women were to die in childbirth, the statistics would be lower.
Dense Breast Tissue
Women with dense breast tissue have a higher chance of developing breast cancer. Dense breast tissue means that the breast has more glandular tissue and less fatty tissue. This is only normally viewable with a mammogram. Unfortunately dense breast tissue also makes it harder for specialists to spot problems with mammogram's.
Women who have had more menstrual cycles because they started their periods before the age of 12 or went through menopause later in life (after 55) have a slightly raised chance of developing breast cancer. This may be related to longer exposure, over a lifetime to the effects of estrogen and progesterone. Women who have their ovaries removed before the age of 45 conversely have slightly lowered risks of developing breast cancer.
Benign Breast Problems
Women who develop other breast conditions may have an increased risk of developing breast cancer. Doctors divide conditions into 3 groups, according to their rate of risk. These are:
Group 1: Non-proliferative Lesions
• Mild hyperplasia
Group 2: Proliferative Lesions Without Atypia
• Complex fibroadenoma
Group 3: Proliferative Lesions With Atypia
• Atypical ductal hyperplasia (ADH).
Xenoestrogens (Foreign Estrogens)
Much research has gone into the possible links between environmental toxins and breast cancer. One area of study concerns certain hormone mimicking chemicals (called xenoestrogens) which are found in plastics, certain cosmetics, pesticides, personal care products and gasoline. Some researchers claim there is no link between these chemicals and breast cancers, while others are worried. One theory suggests that a woman's own natural supply of estrogen, called estradiol, can be converted into 2 types of structures. One structure works to protect against breast cancer, while the other has a negative effect. It may be that exposure to xenoestrogens causes the female body to produce more of the 'bad' estrogens.
Between the 1940s and 1960s some pregnant women were prescribed a drug called diethylstilbestrol (DES) to prevent miscarriage. Both daughter and mother (where the mother was prescribed DES) may have a slightly higher risk of developing breast cancer.
Childbearing patterns seem to have some effect. Women who have their first full term pregnancy after 35 or have no children appear to have a slightly higher risk of developing breast cancer, although this risk increase is very small. Pregnancy reduces the number of menstrual cycles a woman has in a lifetime, which may be one factor. If a woman had her menarche (first period) at the age of 10, was never pregnant and went through menopause at 55, she would face about twice the risk of a woman who began menstruating at 15, had a child before 30 and went though early menopause. Some studies indicate that breastfeeding for a total of 2 years or more may decrease the risk of breast cancer before menopause, but it does not affect the rates after menopause. If you are worried about your risks, check out our list of books on breast cancer, there are some publications specifically about risk assessment. Read also about the benefits of breast feeding for moms.
Some studies indicate that women who use birth control pills have a slightly higher risk of breast cancer than those who do not. However this risk seems to gradually go back to normal when the pills are stopped. For information on preventing the disease, see breast cancer prevention for more advice.
Hormone Replacement Therapy
As hormones play an important role in breast cancer, scientists are keen to better understand the effects of changing hormone balances artificially (that is by both birth control pills and hormone replacement therapy). Hormone replacement therapy is also called HRT, hormone therapy, HT, estrogen replacement therapy and/or progesterone therapy. HRT has been heavily marketed by drug companies who are driving the idea that menopause is a state of hormone deficiency, rather than a natural process. The pros and cons of hormone replacement are discussed here: Estrogen replacement therapy. The use of estrogen therapy alone after menopause does not seem to increase the risk of breast cancer, unless it is used long-term (for more than 10 years). Combined HT on the other hand seems to increase the risk of cancer, as well as a woman's chances of dying from it, after as little as 2 years of use.
Obesity and women: The connection between body weight and breast cancer is complex. Being overweight or obese does appear to increase the risk of breast cancer, particularly after menopause. Fat tissue produces estrogen and excess estrogen has been linked to breast cancer. Overweight women are also more likely to have raised insulin levels which have been linked to some cancers, including breast cancer. The risk seems to be higher however in women who gain weight during adulthood than those who have been overweight since childhood. Furthermore fat in the waist area appears to cause more damage than fat in the hips and thighs. Scientists believe that fat cells in different parts of the body have subtle differences and may react differently. BMI calculator, are you obese?
Many researchers believe that a woman's diet may trigger some of the genetic mutations necessary to cause breast cancer. In particular they point to diets low in fiber and high in fat. Worldwide statistics show the higher the amount of fat in a diet, the higher the rates of breast cancer. One theory is that higher fat diets increase the kind of estrogens related to breast cancer. Beyond these findings, the link remains unclear and there are still conflicting findings. The theory behind high fiber diets is that they offer cancer prevention by allowing food to move swiftly through the digestive tract so they have little chance to cause problems. Scientists are also studying vitamin A, C and E which act as antioxidants stopping free radicals from disrupting the DNA of cells.
Alcohol has been clearly linked to an increased risk of developing breast cancer. Women who drink 1 alcoholic drink a day have a small increase of risk and those who drink 2 to 5 have about 1.5 times more risk. Excessive alcohol also leads to increased risk in other cancers and for this reason, the American Cancer Society recommends that women limit their alcohol intake to no more than one drink a day.
Various new studies show that smoking (even second-hand smoke) may increase the risk of developing breast cancer as well as incidences of breast cancer recurrence. These reports are still preliminary and further research is still necessary.
Lack of Exercise
One study from the Women's Health Initiative (WHI) showed that as little as 1.25 to 2.5 hours a week of physical activity reduces a woman's risk of breast cancer by 18 percent. There is little doubt at this time that exercise is important, the question researchers now want to know is how much is good? The American Cancer Society currently recommends 45 to 60 minutes a day, 5 days a week.
To date research shows no connection between breast implants and breast cancer risk - even if there is some leakage from an implant. However implants can make it harder to see natural breast tissue on a mammogram and any lumps under the implants will be difficult to feel with the fingers. Additional X-ray images called implant displacement views may be offered to women with implants, this will allow examination of the breast tissue more clearly.
Some emails have circulated stating that the chemicals used in underarm antiperspirants are absorbed through the skin and can cause breast cancer. There is little evidence to support this theory. One small study found trace levels of parabens (used as a preservative in antiperspirants and which have weak estrogen-like properties) in a sample of breast cancer tumors. However the study did not look if the parabens actually caused the tumor or whether they simply gathered there after the event. Another large study found no difference in breast cancer rates between women who used underarm antiperspirants and those who did not.
Another email which did the rounds was that bras cause breast cancer by obstructing lymph flow. There is no scientific evidence to support this. The only likely connection is that women who do not need to wear bras are likely to be thinner or have less dense breast tissue, so any lump will be easier to identify.
|Related Articles on Breast Cancer
For more explanation on female cancers, see the following:
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