Breast Cancer Risk Factors

Breast cancer (BC) is the most common type of cancer among women. This is a disease in which malignant (cancer) cells are detected in the tissues of the breast. These cells usually arise from the ducts or the lobules in the breast. The cancer cells can then spread within the breast and to other parts of the body.

There are two big groups of BC risk factors.

Group 1: BC risk factors which we can not control:

1. Gender.

Simply being a woman is the main risk factor for BC. Men can have BC, too, but this disease is about 100 times more common in women than in men. This might be because men have less of the female hormones estrogen and progesterone, which can promote breast cancer cell growth;

2. Age (getting older).

The risk of Breast Cancer increases with age. As you get older, your risk of BC goes up. Most invasive breast cancers (those that have spread from where they started) are found in women age 55 and older.

3. Family history of BC.

It’s important to note that most women (about 8 out of 10) who get BC do not have a family history of the disease, but:

• Women who have close blood relatives with BC have a higher risk of the disease.

• Having a first-degree relative (mother, sister, or daughter) with BC almost doubles a woman’s risk. Having 2 first-degree relatives increases her risk about 3-fold.

• Women with a father or brother who have had BC also have a higher risk of BC.

Overall, less than 15% of women with BC have a family member with this disease.

4. Having a personal history of BC.

A woman with cancer in one breast has a higher risk of developing a new cancer in the other breast or in another part of the same breast. (This is different from a recurrence or return of the first cancer.) This risk is even higher for younger women with BC.

5. Race and ethnicity.

White women are slightly more likely to develop BC than African-American, Asian, Hispanic and Native American women.

6. Certain inherited genes.

About 5% to 10% of BC cases are thought to be hereditary, meaning that they result directly from gene defects (called mutations) passed on from a parent.

The most common cause of hereditary BC is an inherited mutation in the BRCA1 and BRCA2 genes. In normal cells, these genes help prevent cancer by making proteins that help keep the cells from growing abnormally. Mutated versions of these genes cannot stop abnormal growth, and that can lead to cancer. If you have inherited a mutated copy of either gene from a parent, you have a higher risk of BC.

BC linked to these mutations are more often found in younger women and more often in both breasts than cancers not linked to these mutations. Women with these inherited mutations also have a higher risk of developing other cancers, mainly ovarian cancer.

Genetic testing can be done to look for mutations in the BRCA1 and BRCA2 genes (or less commonly in other genes such as PTEN or TP53).

7. Personal menstrual history.

Women who have had more menstrual cycles because they started menstruating early (before age 12) and women who went through menopause later (after age 55) have a slightly higher risk of BC. The increase in risk may because they have a longer lifetime exposure to the hormones estrogen and progesterone.

8. Radiation therapy to the chest for another cancer (such as lymphoma) have a significantly higher risk for BC.

Women who as children or young adults were treated with radiation therapy to the chest for another cancer (such as Hodgkin disease or non-Hodgkin lymphoma) have a significantly higher risk for BC. This varies with the patient’s age when they got radiation. And if you had chemotherapy with the radiation, it might have stopped ovarian hormone production for some time, which lowers the risk. The risk of developing BC from chest radiation is highest if you had radiation during adolescence, when your breasts were still developing. Radiation treatment after age 40 does not seem to increase BC risk.

9. Having dense breast tissue.

Breasts are made up of fatty tissue, fibrous tissue, and glandular tissue. Someone is said to have dense breasts (on a mammogram) when they have more glandular and fibrous tissue and less fatty tissue. Women with dense breasts on mammogram have a risk of BC that is 1.2 to 2 times that of women with average breast density. Unfortunately, dense breast tissue can also make mammograms less accurate.

A number of factors can affect breast density, such as age, menopausal status, the use of certain drugs (including menopausal hormone therapy), pregnancy, and genetics.

8. Certain benign breast conditions.

Women diagnosed with certain benign (non-cancer) breast conditions may have a higher risk of BC. Some of these conditions are more closely linked to BC risk than others. Doctors often divide benign breast conditions into 3 general groups, depending on how they affect this risk.

A) Non-proliferative lesions: these conditions are linked to an overgrowth of breast tissue. They don’t seem to affect BC risk, or if they do, it’s to a very small extent. They include: fibrocystic changes or disease, adenosis (non-sclerosing), benign Phyllodes tumor, a single papilloma, duct ectasia, epithelial-related calcifications, other benign tumors (lipoma, hamartoma, hemangioma, neurofibroma, adenomyoepthelioma).

B) Proliferative lesions without atypia (cell abnormalities): in these conditions there’s excessive growth of cells in the ducts or lobules of the breast. They seem to raise a woman’s risk of BC slightly. They include: ductal hyperplasia (without atypia), fibroadenoma, sclerosing adenosis, papillomatosis, radial scar.

C) Proliferative lesions with atypia: in these conditions, the cells in the ducts or lobules of the breast tissue grow excessively, and some of them no longer look normal. These types of lesions include: atypical ductal hyperplasia (ADH) and atypical lobular hyperplasia (ALH). BC risk is raised in women with these changes.

If a woman has a family history of BC and either hyperplasia or atypical hyperplasia, she has an even higher risk of BC.

9. Exposure to diethylstilbestrol (DES).

From the 1940s through the early 1970s some pregnant women were given an estrogen-like drug called DES because it was thought to lower their chances of losing the baby (miscarriage). These women have a slightly increased risk of developing BC. Women whose mothers took DES during pregnancy may also have a slightly higher risk of BC.

Group 2: BC risk factors which we can control:

1. Obesity.

Being overweight after menopause increases breast cancer risk.

Before menopause ovaries make most of estrogen; fat tissue makes only a small amount. After menopause (when the ovaries stop making estrogen), most of a woman’s estrogen comes from fat tissue. Having more fat tissue after menopause can raise estrogen levels and increase a chance of getting BC. Also, women who are overweight tend to have higher blood insulin levels. Higher insulin levels have been linked to some cancers, including BC.

Still, the link between weight and BC risk is complex. For instance, risk appears to be increased for women who gained weight as an adult, but may not be increased among those who have been overweight since childhood. Also, excess fat in the waist area may affect risk more than the same amount of fat in the hips and thighs.

2. Low physical activity.

Evidence is growing that physical activity in the form of exercise reduces BC risk. The main question is how much exercise is needed. In one study from the Women’s Health Initiative, as little as 1¼ to 2½ hours per week of brisk walking reduced a woman’s risk by 18%. Walking 10 hours a week reduced the risk a little more.

To reduce risk of BC, the American Cancer Society recommends that adults get at least 150 minutes of moderate intensity or 75 minutes of vigorous intensity activity each week (or a combination of these), preferably spread throughout the week.

Moderate activity is anything that makes you breathe as hard as you do during a brisk walk. During moderate activities, you’ll notice a slight increase in heart rate and breathing. You should be able to talk, but not sing during the activity. Vigorous activities are performed at a higher intensity. They cause an increased heart rate, sweating, and a faster breathing rate. Activities that improve strength and flexibility, such as weight lifting, stretching, or yoga, are also beneficial.

3. No having children.

Women who have not had children or who had their first child after age 30 have a slightly higher BC risk overall. Having many pregnancies and becoming pregnant at an early age reduces BC risk overall. Still, the effect of pregnancy is different for different types of BC. For a certain type of BC known as triple-negative, pregnancy seems to increase risk.

4. No breastfeeding.

Some studies suggest that breastfeeding may slightly lower BC risk, especially if it’s continued for 1½ to 2 years. The explanation for this possible effect may be that breastfeeding reduces a woman’s total number of lifetime menstrual cycles (the same as starting menstrual periods at a later age or going through early menopause).

5. Alcohol.

Drinking alcohol is clearly linked to an increased risk of developing BC. The risk increases with the amount of alcohol consumed. Compared with non-drinkers, women who have 1 alcoholic drink a day have a very small increase in risk. Those who have 2 to 5 drinks daily have about 1½ times the risk of women who don’t drink alcohol. Excessive alcohol consumption is known to increase the risk of other cancers, too.

The American Cancer Society recommends that women have no more than 1 alcoholic drink a day. A drink is 12 ounces of regular beer, 5 ounces of wine, or 1.5 ounces of 80-proof distilled spirits.

6. Hormone-replacement therapy after menopause;

Hormone therapy with estrogen (often combined with progesterone) has been used for many years to help relieve symptoms of menopause and help prevent osteoporosis (thinning of the bones). This treatment goes by many names, such as post-menopausal hormone therapy (PHT), hormone replacement therapy (HRT), and menopausal hormone therapy (MHT). There are 2 main types of hormone therapy. For women who still have a uterus (womb), doctors generally prescribe estrogen and progesterone (known as combined hormone therapy or HT). Progesterone is needed because estrogen alone can increase the risk of cancer of the uterus. For women who’ve had a hysterectomy (those who no longer have a uterus), estrogen alone can be used. This is known as estrogen replacement therapy (ERT) or just estrogen therapy (ET).

Combined hormone therapy (HT): use of combined hormone therapy after menopause increases the risk of BC. It may also increase the chances of dying from BC. This increase in risk can be seen with as little as 2 years of use. Combined HT also increases the likelihood that the cancer may be found at a more advanced stage. (This means it’s already spread from the place it started when it’s found.)

A woman’s BC risk seems to return to that of the general population within 5 years of stopping treatment.

Estrogen therapy (ET): The use of estrogen alone after menopause does not seem to increase the risk of BC much, if at all. But when used long term (for more than 10 years), ET has been found to increase the risk of ovarian and BC in some studies.

At this time there are few strong reasons to use post-menopausal hormone therapy (either combined HT or ET), other than possibly for the short-term relief of menopausal symptoms. ET does not seem to increase BC risk, but it does increase the risk of stroke.

The decision to use HT should be made by a woman and her doctor after weighing the possible risks and benefits (including the severity of her menopausal symptoms), and considering her other risk factors for heart disease, BC, and osteoporosis.

7. Birth-control pills and shot.

Oral contraceptives: studies have found that women using oral contraceptives (birth control pills) have a slightly higher risk of BC than women who have never used them. Once the pills are stopped, this risk seems to go back to normal over time. Women who stopped using oral contraceptives more than 10 years ago do not appear to have any increased BC risk. When thinking about using oral contraceptives, women should discuss their other risk factors for BC with their health care provider.

Birth control shot: Depo-Provera is an injectable form of progesterone that’s given once every 3 months as birth control. A few studies have looked at the effect of birth control shots on BC risk. Women currently using birth control shots seem to have an increase in BC risk, but it appears that there is no increased risk in women 5 years after they stop getting the shots.

8. Smoking.

More studies have shown that heavy smoking over a long-time is linked to a higher risk of BC. The risk was highest in certain groups, such as women who started smoking before they had their first child.

Researchers are also looking at whether secondhand smoke increases the risk of BC. Both mainstream and secondhand smoke contain chemicals that, in high concentrations, cause BC in rodents. Studies have shown that chemicals in tobacco smoke reach breast tissue and are found in breast milk of rodents. Tobacco smoke may have different effects on BC risk in smokers compared with those who are just exposed to secondhand smoke.

A report from the California Environmental Protection Agency in 2005 concluded that the evidence about secondhand smoke and BC is “consistent with a causal association” in younger, mainly pre-menopausal women. In any case, this possible link to BC is yet another reason to avoid secondhand smoke.

9. Night work.

Some studies have suggested that women who work at night might have an increased risk of BC (ex., nurses on a night shift). Some researchers think the effect may be due to changes in levels of melatonin, a hormone that’s affected by the body’s exposure to light, but other hormones are also being studied.

All women with risk factors of BC have to visit their Breast disease specialists or Medical oncologists regularly.

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