What is breast cancer?
In 2018, breast cancer was the most frequently diagnosed cancer and the second most common cause of cancer deaths in Ontario women. In Ontario, breast cancer usually develops later in life, with 83 per cent of cases diagnosed in women age 50 and older.
In Ontario, breast cancer usually develops later in life, with 83 per cent of cases diagnosed in women age 50 and older.
Men can also get breast cancer, but it's much less common. The My CancerIQ Breast Cancer Risk Assessment is based only on studies of women, so can't accurately assess breast cancer risk in men.
The female breast is a complex structure. It contains glands that make milk (lobules), tubes to carry milk from the lobules to the nipple (ducts), fibrous supportive tissue, 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 fibrous scar-like tissue or are fluid-filled sacs or cysts.
If a lump or 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, and lifestyle factors may play a greater role in post-menopausal breast cancer. More research is needed to fully understand the differences between pre- and post-menopausal breast cancer.
Risk factors you can change or control
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Smoking
Although we think of smoking as causing lung cancer, in fact it increases the risk of many types of cancer — including breast cancer. Tobacco smoke contains 70 substances that are known to cause cancer. There is no safe tobacco product and no safe level of smoking.
Alcohol consumption
For breast cancer, there is no safe level of alcohol consumption; even drinking small amounts of alcohol can increase your risk. Alcohol may damage the DNA of cells or allow other cancer-causing substances to more easily enter cells. There is also evidence suggesting that alcohol increases the level of estrogen in the blood, which can stimulate the growth of some tumours.
Adult weight gain
Gaining body fat as an adult may increase the level of several hormones, including estrogen, and may stimulate cell growth. Achieving and maintaining a healthy weight helps to reduce your risk of breast cancer.
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Diet
Some evidence suggests a diet rich in vegetables and fruits may help reduce the risk of breast cancer. The reasons are not yet clear. Vegetables and fruit are good sources of beneficial nutrients such as antioxidants, carotenoids and phytochemicals that help to boost the immune system. Vegetables and fruit can also help to prevent nutritional deficiencies, provide people with natural sources of cancer-fighting vitamins and help people achieve or maintain a healthy weight.
Physical activity
Women who are physically active may have a reduced risk of breast cancer. 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
Oral contraceptives:
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, your 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 your risk of breast cancer. Your risk 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.
Genetics
Genetic mutations
Every cell contains a genetic blueprint in the form of DNA. DNA tells the cell when to reproduce (make new cells) and what to do. A genetic mutation is a permanent change in the DNA of the cell. Mutations can occur by chance when cells reproduce or because of damage to the DNA. Mutations can also be inherited from a parent (i.e., hereditary genetic mutations).
Hereditary genetic mutations that increase a woman's lifetime 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 other cancers, such as ovarian and pancreatic cancer. Mutations in other genes (e.g., TP53, CHEK2, PTEN or CDH1) can also increase the risk of breast cancer.
If you have a first-degree relative (e.g., a parent, brother, sister or child) or multiple relatives (related by blood) who have been tested and 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 to find out more.
Family history
Having a first-degree or multiple "blood" relatives (mother, father, sister, brother, child, grandparent, aunt, uncle, niece or nephew) diagnosed with breast, ovarian and/or prostate cancer - especially if the cancer was diagnosed at a young age – may double your risk of developing breast, ovarian and/or prostate cancer in the family.
Ashkenazi Jewish heritage
Women of Ashkenazi 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.
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Reproductive history - menstruation, menopause, pregnancy and breastfeeding
Hormones, especially estrogen, can encourage the growth of some types of breast cancers. The lifetime exposure to estrogen is lower in women who:
- start menstruating at a later age;
- go through menopause at an earlier age.
In general, starting to menstruate at a younger age 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 children at an earlier age or have several children.
- breastfeed, particularly for a cumulative total of a year or more.
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Breast density
Breast tissue is made up of dense and fatty tissue. Dense tissue, or fibroglandular tissue, is made up of ducts, glands for making milk and supportive tissue. Breast density is measured by how much dense breast tissue a breast has compared to fatty tissue.
Breast density is determined when you get a mammogram. In Ontario, as of July 2021, breast density is reported on OBSP mammogram reports as a percentage, and as a Breast Imaging Reporting and Data System (BI-RADS) category. BI-RADS has 4 breast density categories (A-D) ranging from the least amount of dense tissue to the most amount of dense tissue. People with high breast density have an increased risk of developing breast cancer. Dense tissue can also make it harder to find breast cancer on a mammogram.
Breast density cannot be changed but it can be affected by other factors such as age, menopause and hormone replacement therapy. If you have dense breasts and have concerns about your risk of developing breast cancer, talk with your doctor or nurse practitioner about breast cancer screening recommendations.
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Chest radiation
Radiation therapy is used to treat certain cancers, such as lymphoma, and in the past was used to treat diseases or conditions 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 an increased risk of breast cancer. The risk is higher for women who were treated during puberty.
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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 a new breast cancer or recurrence of a first 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®.
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Height
Studies suggest that women who are taller than 5'7" may have a higher risk of developing breast cancer after menopause. The reasons aren’t clear but may reflect the influence of hormones and other factors that affect growth.
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Weight when you were born
Women who were heavier than average at birth (usually defined as weighing more than 8.5 pounds) may have a slightly higher risk of breast cancer before menopause. The reasons for this are not clear. It may reflect the effect of exposure before birth to higher levels of hormones circulating in the blood of the mother.
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Weight when you were 7 years of age
Women who were overweight at about 7 years of age may tend to have a lower risk of breast cancer. The reasons for this are not clear. It may be because hormone levels that change with weight gain have different effects depending on your age.
What you can do to protect yourself
Screening:
The Ontario Breast Screening Program (OBSP)
The Ontario Breast Screening Program (OBSP) is a screening program designed to encourage women to get screened for breast cancer. The program screens 2 different groups of women who are eligible for breast cancer screening in Ontario: those at average risk and those at high risk.
Women at average risk:
Women who are 50 to 74 years of age, have no symptoms of breast cancer, have not had breast cancer, do not have breast implants and have not had a mastectomy 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.
- Booking of required diagnostic tests with primary care provider 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.
Learn more:
- Cancer Care Ontario - The Ontario Breast Screening Program.
- Cancer Care Ontario - Get Checked for Cancer.
- Call ServiceOntario INFOline at 1-866-532-3161
TTY 1-800-387-5559
Monday to Friday
8:30 am – 5:00 pm - Learn about the First Nations, Inuit, Métis and Urban Indigenous Cancer Strategy (2019-2023).
Women with dense breasts
OBSP participants whose mammogram shows 75% or higher amount of dense breast tissue are asked to come back in 1 year for a mammogram instead of in the usual 2 years.
Learn more
Women at high risk:
The High Risk Ontario Breast 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) (or breast ultrasound if MRI is not medically appropriate). Women can be referred to the High Risk OBSP if they:
- Have gene changes that increase their chance of getting breast cancer (e.g., changes in the BRCA1, BRCA2, TP53, PTEN and/or CDH1 genes);
- Have not had genetic testing, but have had genetic counselling because they have a first-degree family member with gene changes that increase their chance of getting breast cancer (e.g., changes in the BRCA1, BRCA2, TP53, PTEN and/or CDH1 genes);
- Have ≥25 percent lifetime chance of getting breast cancer based on personal and family history (confirmed at a genetics clinic using the International Breast Cancer Intervention Study or CanRisk risk assessment tools); and/or
- Have had radiation therapy to the chest to treat another cancer (e.g., Hodgkin lymphoma) before age 30 and at least eight years ago. For these people, screening would not start before age 30. Below are a few scenarios demonstrating when someone would be eligible for the High Risk OBSP, depending on how old they were when they received radiation therapy to the chest.
- someone who is 35 and had radiation therapy to the chest at age 29 would be eligible for the High Risk OBSP at age 37;
- someone who is 26 and had radiation therapy to the chest at age 18 would be eligible for the High Risk OBSP at age 30; and
- someone who is 40 and had radiation therapy to the chest at age 31 is not eligible for the High Risk OBSP based on this criterion.
- OBSP screening for women at high risk.
- If you don't have a primary care provider, you can register for one at HealthCare Connect or by calling 1-800-445-1822 (Monday to Friday 9 am - 5 pm).
The High Risk OBSP requires a referral from a primary care provider.
Learn more:
Be breast aware
The OBSP 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 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.
Learn more:
Genetic testing
Genetic testing can check to see if you have a genetic mutation that increases your risk of breast cancer. Genetic testing may be 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.
Learn more
- Please speak to your doctor or nurse practitioner to see if genetic testing is appropriate for you. For more information on genetic testing, please visit the Canadian Cancer Society's website.
- Learn more about the High Risk OBSP and services.
If you take artificial hormones, talk with your doctor or nurse practitioner
The artificial hormones in oral contraceptives and hormone replacement therapy may increase your risk of breast cancer. If you take either medication, talk with your doctor or nurse practitioner about both the risks and benefits of treatment.
Limit your alcohol
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 drink less frequently.
Tips for cutting back
- Set aside more days each week as non-drinking days.
- Plan ahead on how you will reduce your alcohol consumption or handle the urge to drink.
- Know the standard drink sizes to accurately track how much you drink.
- Switch to non-alcoholic drinks after you have reached your limit.
If you have trouble cutting down or quitting, there are lots of free resources to help.
Learn more
- The Canadian Cancer Society - Limit Alcohol.
- For help with alcohol addiction: ConnexOntario - Health Services Information for Ontarians.
- Ontario Health's quality standard on Problematic Alcohol Use and Alcohol Use Disorder.
Be smoke-free
If you're not a smoker, then congratulate yourself for avoiding an important cancer risk factor. To keep yourself safe, also try to avoid exposure to other people's tobacco smoke (second-hand smoke).
Smokers have probably heard that quitting will help to improve their health and reduce the risk of cancer and other serious diseases. The good news is that it's never too late to benefit from breaking the habit and becoming smoke-free.
It can appear hard to quit smoking and sometimes it takes more than one attempt, but more than two-thirds of Canadians who were once smokers have been able to butt out. Six out of ten used a smoking cessation aid, such as nicotine replacement therapy, quit smoking programs, or medication. Talk with your doctor, nurse practitioner or pharmacist about the many options out there to help people become smoke-free.
Some tips if you're a smoker who is considering quitting
- Write down or think about how you would feel if you could quit. For example, would you feel better about yourself and more in control of your life? Would it make you a better role model to your children or loved ones? Would it give you a better chance of living to enjoy a healthy retirement? Think about what your life would be like if you could quit and your reasons for wanting to stop.
- Keep track of your smoking. Sometimes, just seeing how much they are smoking — and being more aware of when they are reaching for a cigarette — can help people to cut back. Keep a count of every cigarette you smoke on your cell phone, on a piece of paper, or on your computer.
- Book an appointment with your doctor or nurse practitioner or talk with your pharmacist about smoking cessation aids and programs that might make it easier for you to quit. Investigate all your options so you can think about what you may do in the future.
- Planning is the key to success. Develop a plan for how you will quit (cutting down, cold turkey, or using a smoking cessation aid), when you will start (your quit date), and who will help you and be your quit smoking buddy or coach. Your quit smoking buddy or coach should be someone who will be sympathetic but firm to help you stay on track.
- Knowing how much your habit is costing you may give you motivation to quit. Find out with the Healthy Canadians Cost Calculator.
Learn more about how to become and stay tobacco-free or how you can help someone you care about to quit:
- Speak to a Care Coach at Health811 for quit smoking support by calling 811, TTY 1-866-797-0007.
- Visit Smokers' Helpline to connect with online group of other quitters, Quit Coaches, and additional resources. You can also text iQuit to the number 123456 (in Ontario) for quit support.
- The Ontario Ministry of Health's Quit Smoking website.
- Health Canada's On the Road to Quitting program.
- Visit QuitMap.ca to find a quit smoking counsellor or group in your community.
- Make Your Home and Car Smoke-Free.
- Visit the Indigenous Tobacco Program website to access resources for First Nations, Inuit, Métis and urban Indigenous peoples.
Eat a healthy diet
Studies suggest that a diet high in vegetables and fruit may help to reduce the risk of breast and other cancers. It can also help reduce your risk of other serious chronic diseases, such as diabetes and heart disease.
Tips
- Keep a bowl of fruit in the kitchen so you can easily grab one when hungry or while leaving the house.
- Challenge yourself or your family to try a new vegetable or fruit each week.
- In the morning, add fruit to your cereal or yogurt or vegetables to your omelette.
- Add crushed pineapple to coleslaw or add orange sections or grapes in a tossed salad.
- For dessert, have baked apples or pears or a fruit salad.
- Pull out your blender and make fruit smoothies by blending fat-free or low-fat yogurt or milk with fresh or frozen fruit.
- During the summer and fall, support local farmers by buying fruit at a farmer's market or road-side stand. To add some activity to your day, visit pick-your-own farms.
- Remember that frozen vegetables and fruit with little or no added sugar, fat or salt can be economical and healthy options.
Learn more:
- Visit UnlockFood.ca to get tips for planning meals and snacks, portion sizes, and healthy recipes to try at home.
- Call Health811 at 811 (TTY 1-866-797-0007) to speak to a Registered Dietitian for free.
Maintain a healthy weight
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.
The National Weight Control Registry is a database of thousands of people who have been successful at reaching and maintaining a healthy weight. Reports from the members show that tried-and-true methods include:
- Cutting down on portion sizes, eating a variety of vegetables and fruit and avoiding high-fat foods.
- Eating at regular intervals throughout the day (78% report they eat breakfast every day).
- Tracking your weight regularly (75% say they weigh themselves at least once a week).
- Regular physical activity. The most common form of activity was walking and many reported breaking their activity into chunks throughout the day or incorporating it into their everyday routine, such as walking to work.
Learn more:
- Get tips for healthy weight management at UnlockFood.ca.
- You can speak for free with a Registered Dietitian by calling Health811 at 811 (TTY 1-866-797-0007) . Ask about programs or resources available in your community or through your local Public Health Unit.
- Find out about Body Mass Index and the relationship between weight and health at Canadian Cancer Society's website.
Be physically active
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.
Tips
- 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.
Learn more:
- Public Health Agency of Canada - Being Active.
- ParticipACTION.
- Canadian Society for Exercise Physiology - 24-Hour Movement Guidelines.
- If you haven't been active for a while, you may want to complete the Get Active Questionnaire and discuss the results with your doctor or nurse practitioner.
