Breast Cancer Screening

The Ontario Breast Screening Program (OBSP) is a free, province-wide initiative designed to detect breast cancer early, when it is easier to treat. Early detection can significantly reduce breast cancer deaths by identifying the disease before it spreads. The OBSP offers regular screening mammograms every 2 years (unless advised otherwise by your health care provider) to women, Two-Spirit people, trans people, and nonbinary people aged 40 to 74 who meet the following eligibility criteria:

• No current breast cancer symptoms
• No personal history of breast cancer
• No history of mastectomy (surgery to remove breast tissue)
• No screening mammogram in the past 11 months
• If transfeminine, have used feminizing hormones for at least 5 years in a row

For individuals age 40 to 49. Making an informed decision about whether to get screened is important because generally, people in this age group have a lower chance of getting breast cancer than people ages 50 to 74. Talking to your family doctor, your nurse practitioner, or a Health811 navigator is an important part of making an informed decision about whether breast cancer screening is right for you.

What are the Potential Benefits of Regular Breast Cancer Screening?

Getting screened regularly can find breast cancer earlier which may mean that:

• the chance of dying from breast cancer is lower
• treatment may has a better chance of working
• fewer treatments may be required and the treatments may be less invasive (easier to handle)

What are the Potential Risks of Regular Breast Cancer Screening?

• False-positive: Getting an abnormal result when there is no cancer present. It can lead to extra testing, like a biopsy (taking a small sample of tissue), that can cause anxiety and stress for some people.
• False-negative: Missing a cancer on a screening mammogram, which could lead to delayed treatment.
• Overdiagnosis: Finding a cancer that would not otherwise cause health problems, that may lead to unneeded surgery or treatment.

What Happens During a Mammogram?

• A medical radiation technologist (someone who is trained to take mammograms) will place your breast on the mammography machine.
• A plastic plate will move down slowly to press the breast and hold it in place.
• There will be some pressure for a few seconds on the breast, much like a tight blood pressure cuff. This pressure does not harm your breast tissue. The person taking the mammogram is trained to make sure the experience is as comfortable as possible and will be able to adjust the pressure if needed.
• Mammograms are taken of each breast from 2 different angles.
• The appointment usually takes about 15 minutes.

How Can I Get Screened?

If you decide that breast cancer screening is right for you, you can make an appointment for a mammogram. You do NOT need a referral or order, from your doctor or nurse practitioner to get screened. 

What Happens After the Test?

What Does an Abnormal Mammogram Result Mean?

An abnormal mammogram does NOT necessarily mean you have breast cancer. Many people (9 out of 10 people) with an abnormal result will NOT have breast cancer. However, you need to get more tests to determine the cause of the abnormal result, which may include:

• Additional mammography (extra images or views of the breast)
• Breast ultrasound (sound waves used to look for abnormalities)
• Breast MRI (magnetic resonance imaging to view the breast tissue in more detail)
• Biopsy (removal of a small tissue sample for further testing)

These tests help doctors get a clearer picture and make sure any issues are properly assessed.

Should I Participate in Screening During Pregnancy and Lactation?

Screening with mammography during pregnancy is safe and effective. If you do not want to get screened while you are pregnant, you can start screening 3 months after giving birth, even if you are still lactating.

How Can I Prevent Breast Cancer?

Useful Resources