Breast cancer risk Factors
A risk factor is something, such as a behavior, a substance or a condition, that increases the risk of the onset of cancer. Most cancers are attributable to many risk factors, but breast cancer sometimes appears in women who do not have any of the risk factors described below.
Most breast cancers affect women. This is mainly because their mammary cells are exposed to female hormones called estrogen and progesterone. These hormones, especially estrogen, are related to breast cancer and they promote the growth of some of these cancers.
Breast cancer occurs more frequently in high-income developed countries, such as Canada, the United States and some European countries. The risk of having this type of cancer increases with age. Breast cancer is mainly observed among women aged between 50 and 69 years.
There is convincing evidence that the following factors increase your risk of breast cancer.
Personal History of breast cancer
Women who have already had breast cancer are at higher risk of still having breast cancer. The new cancer can take birth in the same breast as the first cancer or in the other breast. Women who have had ductal carcinoma in situ (DCIS) or lobular carcinoma in situ (CLIS) are more likely to have a second breast cancer, but most of them will not be diagnosed with breast cancer again.
Learn more about ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (CLIS).
Family history of breast cancer and other cancers
When there is a family history of breast cancer, it means that one or more close relatives by blood have or have had this type of cancer. Sometimes there are more cases of breast cancer in some families than you would expect by chance. Sometimes it is not clear whether this family provision is attributable to chance, to a way of life that family members have in common, to genes passed from parents to their children or to an association of these factors.
The risk of breast cancer is higher in the following situations:
One or more of a first-degree parent (mother, sister or daughter) had breast cancer, especially if the diagnosis was made before menopause
Second-degree relatives (grandmother, aunt or niece), on the father's side or on the mother's side, had breast cancer
One parent had cancer in both breasts (bilateral breast cancer) before menopause
2 or more parents had breast or ovarian cancer
One parent had breast cancer and ovarian cancer
A male parent had breast cancer
A woman whose first-degree parent has had breast cancer is about twice as likely to be affected. The more first-degree relatives with breast cancer, the greater the risk. The risk is not as high when it comes to second-degree parenting.
Learn more about genetic risk and cancer.
Mutations of BRCA genes
Genetic mutations are changes that occur in a gene. There are some that can increase the risk of developing certain types of cancer. Hereditary genetic mutations are transmitted from one parent to a child. Only a small number of breast cancers (about 5-10%) are attributable to hereditary genetic mutation.
Breast cancer gene 1 (BRCA1) and breast cancer gene 2 (BRCA2) are normally present in the body. They are called tumor suppressor genes because they seem to play a role in controlling the growth of cancer cells. The presence of mutations in the genes BRCA1 and BRCA2 can make them unable to control the development of cancer. These mutations are rare, affecting about 1 person on 500.
Man and woman may inherit a mutated BRCA gene from their mother or father. People carrying this genetic mutation can also pass it on to their children. If the mutation is present in one of the two copies of a BRCA gene of the father or mother, the risk of a child inheriting this genetic mutation is 50%. This also means that the child has a 50% chance of not inheriting the mutation.
The likelihood that breast or ovarian cancer is linked to an inherited mutation of the BRCA1 or BRCA2 gene is highest in families where:
Several members have been diagnosed with breast or ovarian cancer;
At least one parent was diagnosed with breast cancer before the age of 50 years;
A relative has been diagnosed with breast cancer and ovarian cancer;
Members were diagnosed with cancer in both breasts;
A man has been diagnosed with breast cancer.
Studies show that women with hereditary mutations in the BRCA1 or BRCA2 gene have up to 85% risk of being diagnosed with breast cancer. These women also have a higher risk of having breast cancer at a younger age, usually before menopause. A mutation in the BRCA gene also results in an increased risk of cancer in both breasts. If the cancer appears in a breast, they are more likely to see the disease manifest in the other breast. In addition, mutations in BRCA genes increase the risk of ovarian cancer onset at any age.
If you have multiple family members with breast cancer, talk to your doctor about hereditary breast cancer and genetic testing.
Some genetic disorders
There is a link between the rare hereditary genetic disorders that follow and an increase in the risk of breast cancer.
Li-Fraumeni syndrome increases the risk of developing certain types of cancer, such as breast cancer, osteosarcoma, soft tissue sarcoma and leukemia. Most people with Li-Fraumeni syndrome exhibit a mutation in the TP53 gene, which is normally a tumor suppressor gene.
Telangiectasia ataxia (AT) is caused by a mutation in the ATM gene. This gene is responsible for repairing DNA that is damaged. Some families with high breast cancer have mutations in this gene.
Cowden syndrome is caused by a mutation of the PTEN gene, which is normally a tumor suppressor gene. People with this disorder are more likely to have breast cancer, gastrointestinal cancers and thyroid gland cancer.
The Jeghers syndrome can be linked to a mutation of the STK11 gene, also called LKB1. This gene normally seems to act as a tumor suppressor gene. Jeghers syndrome increases the risk of gastrointestinal cancers and breast, ovarian and testicular cancers.
Other genetic mutations
There is a link between the following genetic mutations and an increase in the risk of breast cancer.
A mutation in the CHEK2 gene was observed in some families with Li-Fraumeni syndrome. CHEK2 is normally a tumor suppressor gene. When he has undergone a mutation, he increases the risk of breast cancer.
When the PALB2 gene is mutated, it suffers a loss of function. It usually protects against breast cancer by helping to repair the changes caused to the DNA and preventing the tumor from growing. When this gene malfunctions, the risk of breast cancer increases.
Ashkenazi Jewish descent
Women of Ashkenazi Jewish descent are more likely to have breast cancer because they are more susceptible to mutations in the BRCA1 and BRCA2 genes. About 1 Ashkenazi Jewish woman on 40 is carrying a mutation of a BRCA gene, compared to 1 female of the general population on 500.
Thick Breasts
Dense breasts contain more connective tissue, glands, and ducts channels than fatty tissue. The density of the breast is a hereditary trait. According to some studies, women with a minimum of 75% of their breast tissue are more than 4 to 6 times more likely to have breast cancer than women with little or no dense breast tissue.
Breast density can only be observed at mammography, but dense breasts make it more difficult to read the shot (image obtained). The adipose tissue appears dark while the dense tissue appears white, as well as tumors, which can mask cancer.
History of reproduction
Estrogen is the main hormone associated with breast cancer. Estrogen affects the growth of breast cells. Experts believe that it also plays an important role in the development of breast cancer cells. The type of exposure and the duration of exposure of these cells to estrogen have an effect on the risk of breast cancer.
Early menstruation
Menstruation is early when they start at a young age, like 11 years old or earlier. If you have been menstruating early, your cells will be exposed to estrogen and other hormones for a longer period of time, which increases the risk of breast cancer.
Late Menopause
Menopause occurs when the ovaries stop making hormones and hormone levels, especially estrogen and progesterone, decrease, thus causing the cessation of menstruation. Menopause that begins at an advanced age, after 55 years, increases the duration of exposure to estrogen and other hormones, increasing the risk of breast cancer. Similarly, a menopause that occurs at a young age decreases the duration of exposure of mammary tissue to estrogen and other hormones. A link between early menopause and a reduction in the risk of breast cancer has been established.
Late pregnancy or absence of pregnancies
The pregnancy interrupts the exposure of the mammary cells to circulating estrogen and also reduces the total number of menstrual cycles of the woman during her life.
Women who lead their first term pregnancy after 30 years present a slightly higher risk of breast cancer than women who have conducted at least one first term pregnancy at a younger age. Getting pregnant at a young age, like before 20 years, reduces the risk of breast cancer.
The more a woman carries children, the more she is protected from breast cancer. Not wearing children at all (nulliparity) increases the risk of breast cancer.
Exposure to ionizing radiation
Women who received radiation therapy in the area of the thorax, neck and armpit (a mantle irradiation field) are more likely to have breast cancer.
This increase in risk was observed especially among women who had received this treatment for Hodgkin's lymphoma. The risk of breast cancer is increased if a mantle radiotherapy is administered to treat Hodgkin's lymphoma in a woman under 30 years of age and is even higher if the treatment was administered during puberty. There is a very high risk of breast cancer if chemotherapy and radiotherapy were administered as a treatment for Hodgkin's lymphoma before the age of 15 years. But in general, the benefits of treating cancer greatly outweigh the risk of having secondary cancer as a result of radiation therapy.
In the past, medical radiation was used to treat health problems such as tuberculosis, acne and swelling of the thymus. Women who have received radiation therapy in the thorax area for these illnesses are more likely to have breast cancer.
Women who were exposed to ionizing radiation during atomic bomb explosions during World War II also have a higher risk of breast cancer, especially if exposure occurred during puberty.
Many women fear that regular mammography will increase their risk of breast cancer. However, modern mammography devices use very low doses of radiation compared to those that are administered to treat cancer. The benefits of mammography exceed the risks of exposure to radiation.
Hormone replacement Therapy
Research shows that the prolonged use of hormone replacement therapy (HRT), especially estrogen-based and progestin (also called combined HRT), increases the risk of breast cancer.
The researchers looked at the data from many studies. Their analysis showed an increased risk of breast cancer in current or recent users of a combined HRT for 5 years or more.
The results of the women's Health Initiative (WHI) Study revealed that the risk of breast cancer increased by about 1% for each year that a woman had taken only estrogen and about 8% for each year that a woman had followed a combined HRT. The study also revealed a higher risk even for a short-term combined HRT compared to a placebo. The increase in risk seems to disappear a few years after the woman has stopped following a HTS.
The WHI study also showed that a significant decrease in the rate of new breast cancer cases among Canadian women aged 50 to 69 years, between 2002 and 2004, coincided with a decrease in the use of combined HRT. This decline has also been observed in many countries, including the United States, Australia, Germany, the Netherlands, Switzerland and Norway. Researchers now believe that the risks of long-term use of combined HRT outweigh the benefits.
Learn more about Hormone replacement therapy (HRT) and the women's Health Initiative (WHI) study.
Contraceptives
Oral contraceptives containing estrogen and progesterone slightly increase the risk of breast cancer, especially for women who have used oral contraceptives for 10 years or more. The increase in risk disappears once the woman has stopped taking oral contraceptives. However, current and recent users (less than 10 years since the last use) see their risk slightly increasing compared to women who have never taken oral contraceptives.
Atypical hyperplasia
Atypical hyperplasia is a non-cancerous (benign) condition characterized by an increased number of abnormal (atypical) cells in the mammary tissue. Women with atypical hyperplasia are more likely to have breast cancer.
Alcohol
Alcohol consumption increases the risk of breast cancer. Even a low alcohol consumption (just over 1 drink per day) can increase the risk of a woman. The risk increases depending on the amount of alcohol consumed.
One of the reasons that may explain the relationship between alcohol consumption and breast cancer is that alcohol is likely to increase estrogen levels. Alcohol may also reduce the amount of certain essential nutrients that protect against cellular damage, such as folic acid (type of vitamin B) and vitamins A and C.
Obesity
Obesity increases the risk of breast cancer in postmenopausal women. Studies show that women who have never followed hormone replacement therapy and whose body mass index (BMI) is 31.1 or more are at 2.5 times more likely to have breast cancer than those with a BMI of 22.6 or less.
Ovarian hormones, especially estrogens, play an important role in the onset of breast cancer. It is believed that many of the risk factors for breast cancer are attributable to the overall dose of estrogen that the breast tissue receives over time. The ovaries produce most of the estrogen, but after menopause, the fatty tissue produces a small amount of estrogen. If you have a lot of fatty tissue, then estrogen levels can increase and thus increase the risk of breast cancer.
Learn more about body weight and the risk of cancer.
Physical inactivity
Physical inactivity increases the risk of breast cancer in women premenopausal or postmenopausal. A number of studies are currently focused on the role of exercise in the onset of breast cancer.
High socio-economic status
The risk of breast cancer is a little greater for women with high incomes. It is possible that it is because of certain aspects of the lifestyle that are related to breast cancer, such as carrying children at a more advanced age or wearing less.
Large size in adulthood
Research shows that the risk of breast cancer after menopause is a little higher for women who are large. It seems that the factors responsible for this increase in risk are energy intake and early-life food, which affect size in adulthood, rather than being large.
It is also possible that large women are more likely to have breast cancer before menopause, but further research is required to confirm this possibility.
Possible risk factors
There is a link between the following factors and breast cancer, but there is not enough evidence to say that they are risk factors. More research needs to be done to clarify the role of these factors in the onset of breast cancer.
Weight Gain in adulthood
Some observations are consistent with the probable link between adult weight gain and breast cancer at postmenopausal. It is not yet certain that weight loss would reduce the risk of breast cancer.
Smoking and second-hand smoke
Recent studies show that active smoking is related to breast cancer in both the premenopausal woman and the postmenopausal woman. There is also a link between second-hand smoke and breast cancer, especially among young, especially premenopausal women who have never smoked. There is insufficient evidence to establish a link between second-hand smoke and the risk of breast cancer in postmenopausal women.
More research is needed to determine the impact of active smoking and second-hand smoke on the rate of new cases of breast cancer, mortality rates and the link between genetics and the risk of smoking.
Birth weight
Some data suggest that higher birth weight may increase the risk of breast cancer before menopause. Higher birth weight means that the fetus is exposed to more estrogen during pregnancy, which could increase the risk of having breast cancer later in life.
Night work
Researchers believe that night work and exposure to artificial light that results in it lowers the level of melatonin in the body. In women, melatonin has the effect of reducing the amount of estrogen in the body and could thus slow the growth of breast cancer cells. Some studies suggest that women who work by shifts, especially at night, have a slightly higher risk of breast cancer. Other studies have shown that there is no increase in risk.
Certain non-cancerous conditions of the breast
Most non-cancerous, or benign, conditions in the breast do not increase the risk of breast cancer. But there could be a link between some of these ailments and the family history of breast cancer. Some non-cancerous conditions in the breast may cause a slight increase in the risk of breast cancer in women when linked to an increase in the number (excess growth) of cells. The following non-cancerous conditions may increase the risk of breast cancer:
Fibrocystic changes in the breast
Hyperplasia
Fibroadenoma Complex
Adenosis
Papillomatosis
Radial scar
No connection to Breast cancer
Important evidence shows that there is no connection between antiperspirants, deodorants, abortion, breast implants or bras and increased risk of breast cancer.
Questions to ask your healthcare team
To make the right decisions for you, ask questions about the risks to your healthcare team.
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