Breast cancer screening guidelines

Cancer screening is testing done on people who may be at risk of getting cancer, but who have no symptoms and generally feel fine. Screening can find breast cancers when they are small, less likely to have spread and more likely to be treated successfully. Women ages 50 to 74 have a lower risk of dying from breast cancer when they are screened regularly with mammograms.

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Screening for Breast Cancer

When to Get Screened

Breast cancer was expected to be the most common cancer diagnosed in Ontario women in 2018. Screening mammography can find breast cancers when they are small, less likely to have spread and more likely to be treated successfully. Your age and family medical history help determine when you should get screened:

If you are age 50 to 74, the Ontario Breast Screening Program (OBSP) recommends that most women in your age group be screened every 2 years with mammography. Find your nearest OBSP site by calling 1-800-668-9304 or visiting Ontario Breast Screening Program locations.
If you are age 30 to 69 and meet any of the following requirements, talk to your doctor about referral to the High Risk Ontario Breast Screening Program:
- You are known to have a gene mutation that increases your risk for breast cancer (e.g., BRCA1, BRCA2, TP53, PTEN, CDH1)
- You are a first-degree relative (parent, brother, sister or child) of someone who has a gene mutation that increases their risk for breast cancer (e.g., BRCA1, BRCA2, TP53, PTEN, CDH1)
- You have a personal or family history of breast or ovarian cancer
- You have had radiation therapy to the chest to treat another cancer or condition (e.g., Hodgkin lymphoma) before age 30 and at least 8 years ago

For every 200 women screened in the Ontario Breast Screening Program, about 18 are referred for further tests and 1 will have breast cancer.

Screening Mammograms

Mammography remains the best screening test for most women. A screening mammogram takes an X-ray picture of the breast and can find breast cancers when they are small, less likely to have spread and more likely to be treated successfully.

Mammograms are considered safe and use a low dose of radiation. The benefits of screening and finding cancer early are more important than any potential harm from the X-ray. Most women will have normal mammogram results.

How Effective Are Screening Mammograms?

Mammograms are the best way to find breast cancer early. But they are not perfect tests. Mammograms may miss some breast cancers. Also, some cancers develop in the time between screens. However, many studies have shown that regular mammograms reduce the risk of dying from breast cancer.

Some breast cancers that are diagnosed through screening may never cause symptoms in a woman during her lifetime (i.e., over-diagnosis). Therefore, some women may have surgery or treatment for a breast cancer that would not have become life threatening.

Not all cancers found at screening can be treated successfully.

To learn more about what happens during a mammogram and how to get ready for a mammogram, see the Mammogram FAQs.

Where to Get Screened

Women ages 50 to 74 can call the nearest Ontario Breast Screening Program location to make an appointment (a doctor’s referral is not needed).

Women in the North West and Hamilton Niagara Haldimand Brant regions may be eligible for screening in one of our mobile screening coaches.

If you think you may be at high risk for breast cancer, talk to your doctor about a referral to the High Risk Ontario Breast Screening Program based on family or medical history.

Ontario Breast Screening Program

The Ontario Breast Screening Program (OBSP) is a province-wide organized screening program that aims to reduce breast cancer mortality through regular screening. The program provides screening for most women ages 50 to 74, and for women ages 30 to 69 who are confirmed to be at high risk of developing breast cancer.

The High Risk OBSP sites help women who may be at high risk of getting breast cancer to undergo genetic assessment. To learn about the eligibility requirements for the High Risk OBSP, see Breast Cancer Screening for Women at High Risk. For women who have been confirmed to be at high risk of getting breast cancer, High Risk OBSP sites offer yearly screening mammograms and breast magnetic resonance imaging (MRI) (or screening breast ultrasound if MRI is not medically appropriate). For women with abnormal screening results, the High Risk OBSP sites coordinate follow-up breast assessments (i.e., any additional tests they need).

Screening Letters Sent to the Public

Cancer Care Ontario sends letters to women turning 50 inviting them to get screened for breast cancer through the Ontario Breast Screening Program. Women ages 51 to 73 who have not been screened in at least 3 years also receive a letter inviting them to get screened.

We also send letters to women ages 50 to 74 reminding them when it is time to return (recall) for screening and informing them of their results, if they are normal.