What Are Four Risk Factors For Breast Cancer

Relative Risks Less Than 1

A relative risk less than 1 means the risk factor lowers the risk of disease.

For example, women who breastfeed for a year have a relative risk of breast cancer of about 0.94 compared to women who dont breastfeed.

You may see:

• Women who breastfeed have a 6 percent lower risk of breast cancer compared to women who dont breastfeed.

Reproductive History Estrogen Is The Main Hormone Associated With Breast Cancer Estrogen Affects The Growth Of Breast Cells Experts Believe That It Plays An Important Role In The Growth Of Breast Cancer Cells As Well The Type Of Exposure And How Long Cells Are Exposed To Estrogen Affects The Chances That Breast Cancer Will Develop

Early menarche

The start of menstruation is called menarche. Early menarche is when menstruation starts at an early age . Starting your period early means that your cells are exposed to estrogen and other hormones for a greater amount of time. This increases the risk of breast cancer.

Late menopause

Menopause occurs as the ovaries stop making hormones and the level of hormones in the body drops. This causes a woman to stop menstruating. If you enter menopause at a later age , it means that your cells are exposed to estrogen and other hormones for a greater amount of time. This increases the risk for breast cancer. Likewise, menopause at a younger age decreases the length of time breast tissue is exposed to estrogen and other hormones. Early menopause is linked with a lower risk of breast cancer.

Late pregnancy or no pregnancies

Pregnancy interrupts the exposure of breast cells to circulating estrogen. It also lowers the total number of menstrual cycles a woman has in her lifetime.

Women who have their first full-term pregnancy after the age of 30 have a slightly higher risk of breast cancer than women who have at least one full-term pregnancy at an earlier age. Becoming pregnant at an early age reduces breast cancer risk.

The more children a woman has, the greater the protection against breast cancer. Not becoming pregnant at all increases the risk for breast cancer.

Obesity And Lack Of Exercise

Gaining weight after menopause can increase a woman’s risk. A 2006 study found that putting on 9.9 kg after menopause increased the risk of developing breast cancer by 18%. Lack of exercise has been linked to breast cancer by the American Institute for Cancer Research.

Obesity has been linked to an increased risk of developing breast cancer by many scientific studies. There is evidence to suggest that excess body fat at the time of breast cancer diagnosis is associated with higher rates of cancer recurrence and death. Furthermore, studies have shown that obese women are more likely to have large tumors, greater lymph node involvement, and poorer breast cancer prognosis with 30% higher risk of mortality.

Weight gain after diagnosis has also been linked to higher rates of breast cancer recurrence or mortality although this finding is not consistent. Weight gain is often less severe with newer chemotherapy treatments but one study found a significant risk of breast cancer mortality in women who gained weight compared to those who maintained their weight. However, other cohort studies and recent clinical trials have not shown a significant relationship between weight gain after diagnosis and breast cancer mortality.

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Factors In The Physical Environment

According to a review, the main mechanisms by which environmental compounds increase breast cancer risk are acting like hormones, especially estrogen, or affecting susceptibility to carcinogenesis. The evidence to date generally supports an association between breast cancer and polycyclic aromatic hydrocarbons and polychlorinated biphenyls . Dioxins and organic solvents, on the other hand, have only shown an association in sparse and methodologically limited studies, but are suggestive of an association. Overall, however, evidence is still based on a relatively small number of studies.

Many xenoestrogens are endocrine disruptors, and potential risk factors of breast cancer.Endocrine disruption is the hypothesis that some chemicals in the body, such as Bisphenol A, are capable of interfering with the production, processing, and transmission of hormones.

A substantial and growing body of evidence indicates that exposures to certain toxic chemicals and hormone-mimicking compounds including chemicals used in pesticides, cosmetics and cleaning products contribute to the development of breast cancer.

The increasing prevalence of these substances in the environment may explain the increasing incidence of breast cancer, though direct evidence is sparse.

Risk Factors For Breast Cancer

Risk factors for breast cancer may be divided into preventable and non-preventable. Their study belongs in the field of epidemiology. Breast cancer, like other forms of cancer, can result from multiple environmental and hereditary risk factors. The term “environmental”, as used by cancer researchers, means any risk factor that is not genetically inherited.

For breast cancer, the list of environmental risk factors includes the individual person’s development, exposure to microbes, “medical interventions, dietary exposures to nutrients, energy and toxicants, ionizing radiation, and chemicals from industrial and agricultural processes and from consumer products…reproductive choices, energy balance, adult weight gain, body fatness, voluntary and involuntary physical activity, medical care, exposure to tobacco smoke and alcohol, and occupational exposures, including shift work” as well as “metabolic and physiologic processes that modify the body’s internal environment.” Some of these environmental factors are part of the physical environment, while others are primarily part of the social, cultural, or economic environment.

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Relative Risks In Research

You can put your knowledge of relative risks to work right away.

Our Breast Cancer Research Studies section has research summary tables on topics ranging from risk factors to treatment to social support.

These tables show research behind many recommendations and standards of care related to breast cancer discussed in this section.

If you dont know how the research process works , our How to read a research table section is a good place to start before looking at the tables.

Learn more about breast cancer research.

New Way To Calculate Breast Cancer Risk May Affect Screening Plansyour Browser Indicates If You’ve Visited This Link

Researchers new breastcancerrisk-prediction model helps translate genetic risks to personalized screening guidelines. Researchers: Alpa Patel, PhD, and Lauren Teras, PhD Institution: American Cancer Society Area of Focus: Population Science The Challenge: About 5% to 10% of breastcancer cases are thought to be hereditary,

American Cancer Society

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Example Of The Impact Of A Relative Risk

Using our example of the exercise study above, we can show how absolute risks affect the number of extra cases.

Inactive women have a 25 percent higher risk of breast cancer than active women .

Since older women are more likely to get breast cancer, a lack of exercise has a greater impact on breast cancer risk in older women than in younger women.

First, lets look at the women in the study ages 70-74 years.

The study finds 500 women per 100,000 who are inactive develop breast cancer in one year. This is the absolute risk for women with the risk factor, lack of exercise.

The study also shows 400 women per 100,000 who are active develop breast cancer in one year. This is the absolute risk for women without the risk factor.

The relative risk is 1.25 for women who are inactive compared to those who are active.

Among women ages 70-74, being inactive led to 100 more cases of breast cancer per 100,000 women in one year .

Now lets look at the women in the study ages 20-29.

The study finds 5 women per 100,000 who were inactive developed breast cancer in one year. And, 4 women per 100,000 who were active got breast cancer.

Here again, the relative risk is 1.25.

However, in women ages 20-29, being inactive led to only 1 extra case of breast cancer per 100,000 women .

So, the same relative risk of 1.25 led to many more extra cases of breast cancer in the older women than in the younger women .

Understanding Your Risk Of Breast Cancer

Several breast cancer risk assessment tools have been developed to help a woman estimate her chance of developing breast cancer. The best studied is the Gail model, which is available on the National Cancer Institutes website at www.cancer.gov/bcrisktool. After you enter some personal and family information, including race/ethnicity, the tool provides you with a 5-year and lifetime estimate of the risk of developing invasive breast cancer. Because it only asks for information about breast cancer in first-degree family members and does not include their ages at diagnosis, the tool works best at estimating risk in women without a strong inherited breast cancer risk. For some women, other ways of determining the risk of breast cancer may work better. For example, women with a strong family history of breast cancer risk should consider talking to a genetic counselor.

It is important to talk with your doctor about how to estimate your personal risk of breast cancer and to discuss risk-reducing or prevention options .

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Age At Menarche And Menopause

Women who start menstruating early in life or who have a late menopause have an increased risk of developing breast cancer. Women who have a natural menopause after the age of 55 are twice as likely to develop breast cancer as women who experience the menopause before the age of 45. At one extreme, women who undergo bilateral oophorectomy before the age of 35 have only 40% of the risk of breast cancer of women who have a natural menopause.

Obesity Immune Function And Risk Of Cancer

Immune system alterations may be important in the higher incidence rates of cancer in obese patients since obesity has been correlated to a reduced immunocompetence in humans. Moulin et al. have recently shown that severely obese patients have a significantly lower natural killer cell cytotoxic activity as compared to normal individuals matched for age and gender, with lower defence against invaders such as precancerous and cancerous cells . Interestingly, weight loss is responsible for an increase in NK cytotoxic activity after 6 months from gastric bypass surgery . Lynch et al. have recently shown that omental invariant NKT cell frequencies were lower in patients with severe obesity as compared to lean healthy subjects, thus suggesting a novel role for the omentum in immune regulation and tumor immunity .

The following list shows the possible factors involved in the development of cancer in obesity.

Anthropometric parameters:

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Familial Breast Cancercriteria For Identifying Women At Substantial Increased Risk

The following categories identify women who have three or more times the population risk of developing breast cancer

• A woman who has:

• One first degree relative with bilateral breast cancer or breast and ovarian cancer or

• One first degree relative with breast cancer diagnosed under the age of 40 years or one first degree male relative with breast cancer diagnosed at any age or

• Two first or second degree relatives with breast cancer diagnosed under the age of 60 years or ovarian cancer at any age on the same side of the family or

• Three first or second relatives with breast and ovarian cancer on the same side of the family

• First degree relative is mother, sister, or daughter. Second degree female relative is grandmother, granddaughter, aunt, or niece

• Criteria for identifying women at very high risk in whom gene testing might be appropriate

• Families with four or more relatives affected with either breast or ovarian cancer in three generations and one alive affected relative

Risk Factors For Cancer

Risk Factors for Cancer | Did You Know?

Age, weight, exposure to carcinogens, and genetics can increase the risk of developing cancer. Learn more from this Did You Know? video produced by NCI’s Surveillance, Epidemiology, and End Results program.

It is usually not possible to know exactly why one person develops cancer and another doesnt. But research has shown that certain risk factors may increase a persons chances of developing cancer.

Cancer risk factors include exposure to chemicals or other substances, as well as certain behaviors. They also include things people cannot control, like age and family history. A family history of certain cancers can be a sign of a possible inherited cancer syndrome.

Most cancer risk factors are initially identified in epidemiology studies. In these studies, scientists look at large groups of people and compare those who develop cancer with those who dont. These studies may show that the people who develop cancer are more or less likely to behave in certain ways or to be exposed to certain substances than those who do not develop cancer.

Such studies, on their own, cannot prove that a behavior or substance causes cancer. For example, the finding could be a result of chance, or the true risk factor could be something other than the suspected risk factor. But findings of this type sometimes get attention in the media, and this can lead to wrong ideas about how cancer starts and spreads.

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Reproductive Factors And Menstrual History

According to a , getting your first period before the age of 12 or going through menopause after the age of 55 may increase your risk of breast cancer. This has to do with your exposure to the hormone estrogen.

Additionally, not having children, or having your first child after , may also increase your risk.

How To Prevent Alcohol

Alcohol is classified as a Group 1 human carcinogen by IARC. It is causally linked to 7 types of cancer. Besides female breast cancer, it increases the risk of developing oral cavity , pharynx , oesophagus , liver, larynx and colorectum cancers.

There is no safe level of alcohol consumption. The risk of breast cancer increases with each unit of alcohol consumed per day. More than 10% of alcohol-attributable cancer cases in the Region arise from drinking just 1 bottle of beer or 2 small glasses of wine every day. For breast cancer, this is even higher: 1 in 4 alcohol-attributable breast cancer cases in the Region is caused by this amount.

Simply put, alcohol is toxic. It harms every organ while it passes through the body, says Dr Carina Ferreira-Borges, Acting Director for Noncommunicable Diseases and Programme Manager for Alcohol and Illicit Drugs at WHO/Europe. So, it makes perfect sense to limit the amount of consumed alcohol, to find ways to replace alcohol with other beverages and to adopt nationwide policies that help to reduce alcohol consumption.

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Breast Cancer Is A Disease In Which Malignant Cells Form In The Tissues Of The Breast

The breast is made up of lobes and ducts. Each breast has 15 to 20 sections called lobes, which have many smaller sections called lobules. Lobules end in dozens of tiny bulbs that can make milk. The lobes, lobules, and bulbs are linked by thin tubes called ducts.

Each breast also has blood vessels and lymph vessels. The lymph vessels carry an almost colorless, watery fluid called lymph. Lymph vessels carry lymph between lymph nodes. Lymph nodes are small, bean-shaped structures that filter lymph and store white blood cells that help fightinfection and disease. Groups of lymph nodes are found near the breast in theaxilla , above thecollarbone, and in the chest.

See the following PDQ summaries for more information about breast cancer:

• Genetics of Breast and Ovarian Cancer

Clinical Considerations And Recommendations

How should individual breast cancer risk be assessed?

Health care providers periodically should assess breast cancer risk by reviewing the patients history. Breast cancer risk assessment is based on a combination of the various factors that can affect risk Box 1610111213. Initial assessment should elicit information about reproductive risk factors, results of prior biopsies, ionizing radiation exposure, and family history of cancer. Health care providers should identify cases of breast, ovarian, colon, prostate, pancreatic, and other types of germline mutation-associated cancer in first-degree, second-degree, and possibly third-degree relatives as well as the age of diagnosis. Women with a potentially increased risk of breast cancer based on initial history should have further risk assessment. Assessments can be conducted with one of the validated assessment tools available online, such as the Gail, BRCAPRO, Breast and Ovarian Analysis of Disease Incidence and Carrier Estimation Algorithm, International Breast Cancer Intervention Studies , or the Claus model 34.

Is screening breast self-examination recommended in women at average risk of breast cancer, and what should women do if they notice a change in one of their breasts?

Should practitioners perform routine screening clinical breast examinations in average-risk women?

When should screening mammography begin in average-risk women?

How frequently should screening mammography be performed in average-risk women?

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Hormone Therapy After Menopause

Hormone therapy with estrogen has been used for many years to help relieve symptoms of menopause and help prevent osteoporosis . This treatment goes by many names, such as post-menopausal hormone therapy , hormone replacement therapy , and menopausal hormone therapy .

There are 2 main types of hormone therapy. For women who still have a uterus , doctors generally prescribe estrogen and progesterone . Progesterone is needed because estrogen alone can increase the risk of cancer of the uterus. For women whove had a hysterectomy , estrogen alone can be used. This is known as estrogen replacement therapy or just estrogen therapy .

Combined hormone therapy : Use of combined hormone therapy after menopause increases the risk of breast cancer. This increase in risk is typically seen after about 4 years of use. Combined HT also increases the likelihood that the cancer may be found at a more advanced stage.

The increased risk from combined HT appears to apply mainly to current and recent users. A womans breast cancer risk seems to go back down within 5 years of stopping treatment.

Estrogen therapy : Studies of the use of estrogen alone after menopause have had mixed results, with some finding a slightly higher risk and some finding no increase. If ET does increase the risk of breast cancer, it is not by much.

To learn more, see Menopausal Hormone Therapy and Cancer Risk.