What is breast cancer?
In 2012, breast cancer was the most frequently diagnosed cancer and the second most common cause of cancer deaths in Ontario women. The risk of breast cancer increases with age, peaking at age 70-74.
The risk of breast cancer increases with age, peaking at age 70-74.
Although relatively uncommon, breast cancer can occur in men as well. The My CancerIQ Breast Cancer Risk Assessment is based on studies involving only women so cannot give an accurate assessment of the risk of breast cancer in men.
The female breast is a complex structure that contains milk-producing glands (lobules), tubes to carry milk from the lobules to the nipple (ducts), blood vessels, vessels that carry lymph fluid to the lymph nodes (located under the arm, near the collarbone and in the chest behind the breastbone), and fatty tissue.
Most lumps in the breasts are benign, meaning they are not cancerous. Such lumps are caused by scar-like or fibrous tissues or are fluid-filled sacs or cysts.
If a tumour in the breast is malignant it means it has become cancerous. In cancer, the cells divide uncontrollably and can invade surrounding tissue. Cancerous cells can sometimes spread (metastasize) to other parts of the body.
Breast cancer can occur before a woman has stopped menstruating (pre-menopausal breast cancer) or after menopause (post-menopausal breast cancer). Although many of the risk factors for pre- and post-menopausal breast cancer are the same, there is growing evidence suggesting there are differences as well. For example, genetic and other medical factors may have a greater effect on the development of pre-menopausal breast cancer whereas lifestyle factors may play a greater role in post-menopausal breast cancer. More research is required to fully understand the differences between pre- and post-menopausal breast cancer.
Risk factors you can change or control
For breast cancer, there is no “safe limit” of alcohol consumption: even drinking small amounts of alcohol can increase your risk. Compared to no drinks a day, each daily alcoholic drink increases the risk of breast cancer by almost 10%. The ethanol in alcohol may damage the DNA of cells or allow other carcinogenic (cancer-causing) substances to more easily enter cells. In addition, there is evidence suggesting that alcohol increases the level of estrogen in the blood, which can stimulate the growth of some tumours.
In addition to the direct effects of alcohol, women who are heavy consumers of alcohol may have a poor diet. Poor nutrition may contribute to the development of cancer. Supplements such as multivitamins with folate may help compensate for some deficiencies but is no substitute for a healthy diet and avoiding alcohol.
Adult weight gain
Gaining body fat as an adult may increase the level of several hormones, including estrogen, and may stimulate cell growth. There is some evidence that taking hormone replacement therapy (HRT) may help to reduce the risk of post-menopausal breast cancer associated with adult weight gain. However, the best and healthiest way to reduce your risk is to achieve and maintain a healthy weight.
Women who are physically active may have a reduced risk of breast cancer. Studies have shown that the most active women may have a 20% to 30% lower risk than inactive women. The exact reasons aren’t clear. Physical activity may protect against breast cancer by helping to regulate the levels of hormones and steroids circulating in the blood. It may also help people to achieve and maintain a healthy weight.
Prescription medications that contain female hormones
Compared to women who have never taken oral contraceptives (birth control pills), those who do – or who have taken them in the past – may have a greater risk of breast cancer. When you stop taking oral contraceptives, the risk of breast cancer starts to decline. It’s important to talk with your doctor or nurse practitioner about both the risks and the benefits of oral contraceptives.
Hormone replacement therapy (HRT):
Hormone replacement therapy (HRT) may be used to treat the symptoms of menopause such as hot flashes. Taking HRT, especially prolonged use of the combined form containing both estrogen and progesterone, may increase the risk of breast cancer. The risk quickly falls after HRT is stopped. If you are taking HRT, talk to your doctor or nurse practitioner about both the risks and the benefits of this medication.
Risk factors you can't change or control
History of benign breast disease
Many women have non-cancerous (benign) breast conditions, which may appear as irregular lumps or cysts (fluid-filled sacs) in the breast. If your doctor has said you have benign breast disease it means it is not cancer. However some types of benign breast disease may increase your risk of developing breast cancer.
Every cell contains a genetic blueprint in the form of DNA. DNA tells the cell when to reproduce and what to do. A genetic mutation is a permanent change in the DNA of the cell. Some mutations occur by chance when cells reproduce or because of damage to the DNA. Other mutations are inherited from a parent (i.e., hereditary genetic mutations).
Hereditary genetic mutations that increase a woman’s risk of breast cancer are rare, occurring in less than 1% of the population. When one occurs, however, it can significantly increase a woman’s risk of breast cancer. Probably the best-known mutations are in the BRCA genes (BRCA1 and BRCA2). Having a specific BRCA1 mutation means a woman’s lifetime risk of developing breast cancer is between 55% and 65%; for BRCA2 the risk may be between 45% and 49%. BRCA1 and BRCA2 mutations are also associated with an increased risk of ovarian cancer. Mutations in other genes (TP53, CHEK2, PTEN or CHD1) can also increase the risk of breast cancer.
If you have a “blood” or first-degree relative (e.g., a parent, brother, sister or child) who has been tested and was told they have a known genetic mutation for breast or ovarian cancer, there is a possibility you may also carry the mutation. Talk with your doctor or nurse practitioner.
Having first-degree “blood” relatives (mother, father, sister, brother or child) diagnosed with breast cancer – especially if the cancer was diagnosed at a young age – may double the risk of developing breast cancer. The more close relatives with breast and/or ovarian cancer, the higher the risk.
Ashkenazi Jewish heritage
Women of Eastern European or German Jewish descent are more likely to have genetic mutations that can increase the risk of breast cancer. If you are of Ashkenazi Jewish descent, talk with your doctor about your risk of breast cancer.
Reproductive history - menstruation, menopause, pregnancy and breastfeeding
Hormones, especially estrogen, can encourage the growth of some types of breast cancers. Estrogen levels increase in woman when they go through puberty and start menstruating, change during pregnancy, and drop when breastfeeding (times when women do not menstruate) and after menopause (the cessation of menstruation). As a result, the lifetime exposure to estrogen is lower in women who:
- start menstruating at a later age;
- go through menopause at an earlier age.
Different studies have used different ages to look at the relationship between age of menstruation and the risk of breast cancer. As well, there is some evidence that the typical age of menstruation may be changing in North America. As a rule, though, starting to menstruate at a younger age than most of your peers or going through menopause much later in life is associated with a greater relative risk of breast cancer. Less lifetime exposure to estrogen may help to keep down a woman’s risk of some types of breast cancer.
When women are pregnant, changes occur in the cells of the breast to prepare for breastfeeding. These changes can make the cells more resistant to cancer later in life. The earlier in life a woman experiences these changes, the greater protection she has against breast cancer. As a result, women are at lower risk of breast cancer if they:
- have children, particularly if they:
- have their children at an earlier age or
- have several children.
- breastfeed, particularly for a cumulative total of a year or more.
Radiation therapy is used to treat certain cancers, such as lymphoma, and in the past was used to treat diseases such as tuberculosis, postpartum mastitis, acne or an enlarged thymus gland. Women who received ionizing radiation therapy to the chest before age 30 and at least 8 years ago have a 4% to 6% increased risk of breast cancer. The risk is higher for women who were treated during puberty.
Prescription medications – tamoxifen and raloxifene
Tamoxifen and raloxifene are prescription medications that block the effects of estrogen. They may be prescribed to treat breast cancer, to help prevent breast cancer in women at high risk, or to prevent bone-thinning (osteoporosis). Taking tamoxifen or raloxifene for five or more years may lower your risk of getting breast cancer. These medications have both risks and benefits so they are not appropriate for all women.
Common brand names for tamoxifen include Nolvadex D®, Mylan-Tamoxifen®, Apo-Tamox®, Tamoxifene®, Teva-Tamoxifen®. Brand names for raloxifene include Evista®, Apo-Raloxifene®, Teva-Raloxifene®.
Studies suggest that tall women may have a higher risk of breast cancer. The reasons aren’t clear but may reflect the influence of hormones and other factors that affect growth.
Weight when you were born
Women who were heavier than average at birth (usually defined as weighing more than 8.5 pounds) may tend to have a slightly higher risk of breast cancer before menopause. Why this occurs is not clear. It may reflect the effect of exposure before birth to higher levels of hormones circulating in the blood of the mother.
What you can do to protect yourself
The Ontario Breast Screening Program (OBSP)
Launched in 1990, the Ontario Breast Screening Program (OBSP) is a province-wide, organized breast screening program that provides high-quality breast cancer screening for Ontario women. The program addresses two groups.
Women at average risk:
Women who are 50 to 74 years of age, have no symptoms of breast cancer, no personal history of breast cancer and no breast implants fall into this category. Screening has been shown to be effective when women in this category undergo mammography every two years, starting at age 50. Women over age 74 can be screened within the OBSP but are encouraged to make a personal decision about breast cancer screening in consultation with their doctor or nurse practitioner.
The OBSP provides:
- High-quality mammography in sites accredited by the Canadian Association of Radiologists.
- Well-developed quality assurance at each site.
- Results of the screening appointment for both the woman and her healthcare provider.
- Automatic booking of required diagnostic tests with family physician authorization (if needed).
- A reminder letter when it is time to return for the next screening mammogram.
If you want, you can be referred by your doctor or nurse practitioner. But a referral is not necessary – you can call and book your own appointment.
- Cancer Care Ontario - The Ontario Breast Screening Program.
- Cancer Care Ontario - Get Checked for Cancer.
- Call ServiceOntario INFOline at 1-866-532-3161
Monday to Friday
8:30 am – 5:00 pm
In Toronto 416-314-5518
TTY in Toronto 416-327-4282
- Learn about the Indigenous Cancer Strategy II.
Women at high risk:
The OBSP High Risk Screening program is designed for women aged 30 to 69 years who are identified as being at high risk of breast cancer. It is recommended that these women be screened for breast cancer with annual mammography and breast MRI (magnetic resonance imaging). Women can be referred to the OBSP High Risk Screening Program if they:
- Have been for genetic testing and found to have a genetic mutation that puts them at high risk.
- Have a parent, sibling or child with a genetic mutation that puts them at high risk of breast cancer (i.e., first degree relative of a mutation carrier) and have declined genetic testing themselves.
- Are determined to have a 25% or greater lifetime risk of breast cancer (preferably, assessed at a genetics clinic), which is higher than the risk for the general population of 10-12%.
- Received radiation therapy to the chest before age 30 and at least eight years ago as treatment for another cancer or condition (e.g., Hodgkin’s disease).
The OBSP recommends that women at high risk who are between the ages of 70 and 74 years be screened with mammography only.
The OBSP High Risk Screening program requires a referral from a physician.
- OBSP Screening for women at high risk.
- If you don’t have a doctor, you can register for one at HealthCare Connect or by calling 1-800-445-1822 (Monday to Friday 9 am – 5 pm).
Genetic testing can tell if you have a genetic mutation that increases the risk of breast cancer. Genetic testing is appropriate if you are diagnosed with breast cancer early in life (before age 35) or have a strong family history of breast and/or ovarian or related cancers. The more relatives with a history of cancer and the younger the age at diagnosis, the greater the likelihood that a genetic mutation may be present. The risk of a genetic mutation is also higher for people with a family history of male breast cancer and those who are of Ashkenazi Jewish descent. To determine if you would benefit from genetic testing, talk with your doctor or nurse practitioner.
Please speak to your doctor or nurse practitioner to see if genetic testing is appropriate for you. Learn more about the Ontario Breast Screening Program and services. For more information on genetic testing, please visit the Canadian Cancer Society’s website.
Be breast aware
The OBSP also recommends that all women be breast aware. This means knowing how your breasts normally look and feel so you can tell if there are changes such as:
- A lump or dimpling,
- Changes in your nipple or fluid leaking from the nipple,
- Skin changes or redness that does not go away, or
- Any other changes in your breasts.
Regardless of her age, any woman who notices changes with her breasts or has concerns should see her family doctor or nurse practitioner. Most changes are non-cancerous, but should be checked right away. This is a good time to talk with your doctor or nurse practitioner about regular breast cancer screening, as well as what you can do to reduce your lifetime risk of breast cancer.
If you take artificial hormones, talk with your doctor or nurse practitioner
The artificial hormones in oral contraceptives and hormone replacement therapy may increase the risk of breast cancer. If you take either medication, talk with your doctor or nurse practitioner about both the risks and benefits of treatment.
Research suggests that when it comes to breast cancer, there is no safe level of drinking. To reduce your risk of breast cancer, you may want to stop drinking or reduce your consumption to no more than one drink a day.
Tips for cutting back:
- It’s easier to control what you track. Keep a count of how many drinks you are consuming in a notepad, on your smart phone, or on your computer.
- Know the standard drink size so you can count your drinks accurately.
- Alternate alcoholic and non-alcoholic drinks.
- Plan ahead on how you will reduce your alcohol consumption or handle the urge to drink.
If you have trouble cutting down or quitting, there are lots of free resources to help you from the privacy of your home.
- The Canadian Cancer Society – Alcohol and Cancer.
- For help to stop drinking: ConnexOntario – Health Services Information for Ontarians.
Excess body fat can increase the risk of breast cancer after menopause. The good news is that small changes in diet and physical activity can lead to a modest reduction in weight – and the reduction of breast cancer risk. Making small but consistent changes is a lot safer – and is more likely to lead to long-term success – than going on some extreme diet or weight loss plan.
- Keep a food journal so you are mindful of everything you eat. Your journal can be a small notebook or an app on your smart phone. Throughout the day, write down or enter everything you are about to eat. This may give you time to consider your choices and resist impulses.
- Try to cook and eat at home more often. When you cook it yourself, you can control the amount of fat, sugar and salt. In a restaurant it’s not as easy. For example, in restaurants, vegetables are often sautéed in butter before they are served to improve their look and taste. Additions such as candied walnuts or goat cheese can make the calorie count of a salad skyrocket.
- Using smaller plates can make it easier to eat smaller portions. Portion sizes have ballooned over the years. Visit EatRight Ontario to re-learn what portion sizes should be.
- Make a small change such as switching from whole milk to 1% or skim milk. Do that for a week, until it’s just part of your routine. Then add another small change, such as choosing water over soft drinks. After a week, add another small change. Small changes can add up to a significantly healthier diet.
- Try to avoid eating in front of the TV or computer. If you’re distracted, you may end up eating more than you realize. Make it a point to sit down at your kitchen or dining room table when you eat. Eat slowly and focus on enjoying your food. And most importantly – stop eating as soon as you start to feel full. Avoid eating just for the sake of eating.
- Spend less time sitting in front of the TV and more time walking or working out. Can’t get away from the TV? Then do exercises during the commercials.
Being physically active can help you maintain a healthy weight, reduce your risk of a number of serious diseases, including breast and colorectal cancer, heart disease and diabetes, help to relieve stress and improve mood. Health Canada recommends that adults 18 to 64 years of age be moderately to vigorously active for at least 2.5 hours (150 minutes) a week.
- Think you can’t find the time to be active? For a week, keep track of all the times you missed an opportunity to be active in your everyday life. For example, write down if you took the escalator instead of the stairs, got someone else to do yard work instead of doing it yourself (raking leaves is a form of physical activity), failed to get off the bus one or two stops early so you could walk a few blocks, or drove instead of walking to the mailbox or convenience store. You may find you have more opportunities to be active than you had assumed.
- Try to develop a menu of different activities you enjoy and that build different types of fitness. For example, brisk walking, resistance training and yoga can help to build aerobic capacity, muscular strength and endurance, and flexibility.
- Whenever possible, walk or bike to work, to go shopping, or when moving about your neighbourhood.
- If you dislike exercising alone, involve your partner or family, join a team, find a walking buddy, or take part in sports or recreational activities. Check out your local municipal recreation centre or YMCA/YWCA for classes and groups.
- Make back-up plans for when you face challenges. For example, if the weather means you can’t go walking outside, substitute yoga or resistance training.
- Public Health Agency of Canada – Physical Activity Guide.
- Canadian Society for Exercise Physiology – Physical Activity Guidelines (PDF).
- If you haven’t been active for a while, you may want to complete the PAR-Q form and discuss the results with your doctor or nurse practitioner.