Screening for Breast Cancer

Mammography is a test that uses X-rays to make images (mammograms) of the breasts.

Getting screened regularly with mammography is important because it can find cancer early when it is less likely to have spread to other parts of the body. Treatment may also have a better chance of working when breast cancer is found early.

How effective are screening mammograms?

Mammography is the recommended test for screening women at average risk for breast cancer. It is also recommended for screening women who are eligible for the High Risk Ontario Breast Screening Program along with magnetic resonance imaging (MRI) (or screening breast ultrasound if MRI is not medically appropriate). However, mammography is not a perfect test and may miss some breast cancers. In addition, some cancers may grow in the time between screens. This is why regular screening is important.

To learn more about the effectiveness of mammography see the Mammograms page.

The Ontario Breast Screening Program is a province-wide, organized cancer screening program designed to encourage Ontario women to get screened and lower their chances of dying from breast cancer.

The Ontario Breast Screening 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.

Average risk

If you are age 50 to 74, the Ontario Breast Screening Program recommends that most women in your age group get screened with mammography every 2 years.

You are eligible for screening through the program if you:

• have no new breast cancer symptoms
• have no personal history of breast cancer
• have no current breast implants
• have not had a mastectomy
• have not had a screening mammogram within the last 11 months

High risk

If you are age 30 to 69 and meet the High Risk Ontario Breast Screening Program eligibility criteria, the program recommends that you get screened every year with both mammography and breast magnetic resonance imaging (MRI) (or screening breast ultrasound if MRI is not medically appropriate).

The High Risk Ontario Breast Screening Program does not accept new participants over age 70. However, when participants already in the program turn 70, the program will continue to screen them with mammography only every year until they are age 74.

You are eligible for screening through the High Risk Ontario Breast Screening Program if you:

• have gene changes that increase your chance of getting breast cancer (e.g., changes in the BRCA1, BRCA2, TP53, PTEN or CDH1 genes)
• have not had genetic testing, but have had genetic counselling because you 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 or CDH1 genes)
• have a 25% or greater lifetime chance of getting breast cancer based on personal and family history (confirmed at a genetics clinic using the International Breast Cancer Intervention Study [IBIS] or Breast and Ovarian Analysis of Disease Incidence and Carrier Estimation Algorithm [BOADICEA] risk assessment tools)
• 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 (e.g., a woman who is 35 and had radiation therapy to the chest at age 29 would be eligible for the High Risk OBSP when she is 37)

You must also:

• have valid Ontario Health Insurance Plan coverage
• have a referral from your doctor (referrals from nurse practitioners are not accepted)
• have no new breast cancer symptoms

If you have a personal history of breast cancer or breast implants, you may get screened through the High Risk Ontario Breast Screening Program if you meet program eligibility criteria.

If you are 50 to 74 years old, you can:

• contact your closest Ontario Breast Screening Program location to make an appointment (see Ontario Breast Screening Program Locations or call 1-800-668-9304)
• contact your doctor or nurse practitioner, who can send you for screening

If you are 30 to 69 years old and think you may be at high risk for breast cancer, you should visit your family doctor. They can send you for an assessment or for screening based on your family and medical history.

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 get 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. 

Letters women may receive

• Correspondence privacy notice
• Invitation letter
• Invitation reminder
• Recall letter (2 years)
• Recall reminder
• Normal result letter (1 year recall)
• Normal result letter (2 year recall)
• Normal result letter (no recall)

See a sample of each letter type at Letters to the Public.

Fact sheets

Breast Density Seen on Mammograms

Ontario breast screening brochure

The brochure called “Breast Cancer Screening – it’s never this obvious” provides information on when it is the right time for you to start screening.

Breast Cancer Screening Brochure

Public Health Agency of Canada brochures

• Breast Cancer and Your Risk

Helpful websites

• My CancerIQ
• Canadian Cancer Society