Breast cancer is one of the most common forms of cancer in women. Each year, more than 22,000 women develop breast cancer in Canada and more than 5,000 women die of the disease. Based on current rates, one in nine women in Canada is expected to develop breast cancer during her lifetime.
The risk of getting breast cancer goes up as women get older. The risk of developing breast cancer in the next 10 years is as follows:
- 13 out of 1,000 women in their 40s
- 23 out of 1,000 women in their 50s
- 29 out of 1,000 women in their 60s
- 31 out of 1,000 women in their 70s
Since 1999, the rate of new cases of breast cancer has stabilized, and death rates have steadily declined.
"Please note: the reference numbers in the printed Decision Aid contain some errors. The reference numbers below in the text and the PDF have been corrected."
Risk factors are conditions that may increase your chance of developing breast cancer. Some risk factors are major, while others are minor. It is important to understand that most women will have some of these risk factors.
- A major risk is one that puts you at least twice the risk of breast cancer compared to someone without that risk factor.
- A minor risk is one that put you at less than twice the risk.
Most women will have some of these risk factors
Major risk factors for breast cancer
- Being aged 50 or older.
- Dense breast tissue as shown by a mammogram. Breast density is often lower as women age and after menopause.
- Having a previous breast tissue sample (biopsy) that showed cells that look abnormal (atypical hyperplasia).
- A mother or sister with breast cancer especially if they learned they had breast cancer before age 50. If more than one immediate family member had breast cancer, or if your family has a history of ovarian cancer. Some families may have mutation of a breast cancer gene (a permanent change in the DNA of either of the genes known as BRCA1 or BRCA2).
- Repeated radiation to the chest due to treatment of a disease (such as Hodgkin's). The risk is highest if you were exposed to the radiation between ages 13 to 30.
Minor risk factors for breast cancer
- Not having any children or being more than 30 years old when a first child was born.
- Starting your monthly periods (menstruation) before age 12.
- Late menopause (after age 55).
- Current use of hormone replacement therapy that totals 5 years or more.
- Current use of the birth control pills and for 10 years after you stop taking them.
- Overweight after menopause.
- Having more than one drink of alcohol per day.
f you are not sure about whether you have some of these risk factors, talk to your health care provider.
Although more research is necessary before conclusions can be made, some scientific studies show other risk factors that may be linked to a higher risk of breast cancer including:
- a diet high in fat,
- smoking, or
- being exposed to second-hand smoke.
To get a better sense of your breast cancer risk, you can ask your health care provider or use the Breast Cancer Risk Calculator available on the Public Health Agency of Canada website. This tool uses seven risk factors to predict the risk of breast cancer.
What protects you against breast cancer?
Be aware of the risk factors that you can change. These include your weight, diet, and whether you smoke or drink alcohol. Studies show that women can reduce their risk by being physically active. Women who have given birth to more children and women who breastfed have lower breast cancer risk.
What is breast cancer screening?
Breast cancer screening is an attempt to find cancer even when there may not be any symptoms. The goal is to find breast cancer early, when it is small and less likely to have spread to other parts of the body. This reduces a woman's chance of dying from the disease. The most common method of breast cancer screening is a mammogram.
What is a mammogram?
A mammogram is a medical test that uses x-rays to take pictures of the internal structure of the breast. The testing is also known as "mammography." Mammograms are done for two reasons:
Screening: When women participate on a routine basis to have mammograms done to find breast cancer at an early stage. This type of mammogram looks for signs that breast cancer may be developing, even though no symptoms are there.
Diagnostic: This is typically done to check for breast cancer after a lump or any other sign/symptom has been found such as pain, skin thickening, nipple discharge, or a change in breast size or shape. It may also be used as a second test if a screening mammogram finds something that is not normal.
Here's how a screening mammogram works:
- You will be seated or standing in front of a machine used only for mammograms.
- The x-ray technologist will place your breast onto a plastic plate on the machine. As a second plastic plate is lowered onto the breast, pressure will even out the breast tissue. This allows the machine to get as clear a picture as possible. The tolerance to pressure on the breast varies among women.
- A special low-dose x-ray is then used to look for breast patterns or lumps that are not normal. These may be too small for you or your health care provider to find by feeling your breast.
- The same procedure then occurs with the other breast.
- High quality mammogram finds some breast cancers when they are very small—2 to 4 years before they would be felt.
Are mammograms safe?
Mammograms involve exposure to x-rays and x-ray radiation has been found to cause cancer. The amount of radiation you receive during one screening mammogram will be based on:
- the amount of fat in your breast tissue (density); and
- the number of images taken.
Your total exposure to radiation from screening mammograms will depend on the number of mammograms you have had. X-ray technologists are experts in breast positioning and know how to reduce the amount of radiation you receive. The amount of radiation that you get from a screening mammogram is almost the same as the amount you would receive over 3 months from your usual surroundings (e.g. sun, rocks, soil, buildings, air and food). Studies show that the risk of a new cancer starting due to radiation to the breast from breast screening mammography is extremely low. The benefits of early diagnosis and treatment of breast cancer far outweigh the risk of being exposed to the small amount of radiation from a screening mammogram.
What are the possible benefits and harms of screening mammograms?
The possible benefits and harms linked to breast screening mammograms are listed in the table below. Consider each statement on its own to determine how important each one is to you.
- Peace of mind
- You may feel less worried when you know that you do not have cancer on your screening mammogram.
- Catching cancer at an early stage and simpler treatment
- If your mammogram finds something abnormal, you will be carefully monitored and/or treated. In Canada, more than 97% of breast cancers found by organized screening programs are at an early stage. If your cancer is at an early stage, you may have simpler surgery and less need for chemotherapy.
- Reduced chance of dying from breast cancer
- The purpose of breast screening mammograms is to find breast cancer early. This reduces your chance of dying from breast cancer due to early diagnosis and simpler treatment.
- Cancer may not be found
- Your mammogram may show no signs of an abnormality even though breast cancer is present.
- Extra tests and worry from false alarms
- Some women will have a false alarm because something abnormal is found on mammogram. But after more tests (such as another mammogram, an ultrasound or perhaps a biopsy), no cancer is found. This may take 4 to 6 weeks, causing worry in women. Sometimes, the worry lasts long after the test results are known.
- No improvement to your length and/or quality of life and unnecessary diagnosis
Even though your screening mammogram found breast cancer, your quality of life or the number of years you live may not change. Some breast cancers found by screening would otherwise cause no problems because women would die of something else first. These breast cancers could be slow growing cancers. So, if women with these cancers had not had screening, they might never have known they had cancer and would not have had treatment.
Having a regular screening mammogram
In Canada, experts agree that the benefits of screening mammograms outweigh the harms for women aged 50 to 69. For younger and older women, the balance of benefits and harms is not so clear. Talk to your health care provider about your breast cancer risk and decide what is right for you.
Health officials recommend that women aged 50-69 years have breast screening mammograms once every two years. Note that women aged 40-49 years who choose to have a screening mammogram usually have it done once a year.
The risk of getting breast cancer goes up as you get older
Women who are at higher than average risk of breast cancer (for example, because of a family history of the disease or because they carry a known mutation in either the BRCA1 or the BRCA2 gene) should talk with their health care providers about whether to have mammograms before age 40 and how often to have them.