Breast screening

What this page helps with

A screening mammogram is a low-dose breast X-ray for people without symptoms. This page helps you understand whether routine breast screening applies to you, how Ontario frames the choice at different ages, and how to book it — including without a family doctor. It does not tell you whether you are due; that depends on your last mammogram and any prior results.

Who the routine guidance is for, and who needs another pathway

OBSP screening is for people ages 40–74 who have an Ontario health card, no new breast symptoms, no personal history of breast cancer, no mastectomy, and no screening mammogram in the last 11 months. For transfeminine people, Ontario's published criterion includes at least five consecutive years of feminizing hormone use. Having breast or chest tissue does not by itself establish eligibility.

Ages 40–49. You are eligible to consider screening. Ontario encourages an informed decision, weighing your personal risk, the potential benefits and harms, and what matters to you — the balance can differ from that at 50–74. If screening is chosen, most people are screened every 2 years.

Ages 50–74. Ontario recommends mammography every 2 years for most eligible people. Some people are asked to return sooner because of breast density, family history, previous findings or the radiologist/program recommendation. Follow the interval in your actual OBSP recall letter or your healthcare provider’s plan; not every one-year recall means lifelong annual screening.

High risk. The High Risk Ontario Breast Screening Program (ages 30–69) has separate eligibility criteria. Examples include a confirmed gene variant that increases breast cancer risk, a genetics-clinic assessment of lifetime risk of 25% or more, or radiation to the chest to treat another cancer before age 30 and at least eight years ago. A parent, sibling or child of a confirmed gene-variant carrier may qualify after genetic counselling, even without having genetic testing themselves. Other family histories may call for a genetics assessment first. Family history alone does not automatically establish eligibility. A clinician or genetics service can help arrange the appropriate assessment. See the full High Risk OBSP criteria.

When you need a different plan. A previous breast cancer, an abnormal result awaiting assessment, or current symptoms follow a diagnostic or follow-up pathway set by your clinician. After 74, screening may continue with a referral as an individual decision.

The High Risk program generally uses a mammogram and breast MRI each year, with a referral. A breast ultrasound may be used when MRI is not medically appropriate. Keep any existing high-risk plan rather than switching to the routine two-year pathway.

How to access it in Ontario

For the ordinary OBSP pathway, you can self-refer by calling 1-800-668-9304; no doctor's referral is needed. A family doctor or nurse practitioner can also refer you. If you are 40–49 and unsure, a Health811 navigator (811) can help you weigh the decision. If you have no primary care provider, the program can still screen you; see No family doctor?.

Potential benefits and limitations

Screening can find breast cancer before it can be felt, when treatment may be less intensive and outcomes better. It also has limits: some cancers are missed, some abnormal results turn out not to be cancer (leading to extra imaging or a biopsy), and some cancers found would never have caused harm (overdiagnosis). The balance of benefit and harm differs by age and personal risk, which is why Ontario frames 40–49 as an individual decision. Being "breast aware" — noticing changes and reporting them — is reasonable at any age, but it is not a substitute for screening and no formal self-examination schedule is required.

What the appointment involves

A mammogram takes about 15–20 minutes. Each breast is compressed briefly between plates for two X-ray images. You may feel brief pressure or discomfort in your breast during your mammogram. Let the technologist know if you feel uncomfortable. They can adjust the pressure to help make the experience more comfortable. Results are sent to you and to your provider; OBSP also sends reminders when the next screen is due.

What happens after an abnormal result

Most people with an abnormal screening result do not have cancer. The usual next step is further imaging (extra mammogram views or ultrasound), and sometimes a biopsy. OBSP coordinates this follow-up; do not use a new screening mammogram to investigate a result or a symptom. This page cannot interpret your result.

If you do not have a regular healthcare provider and your mammogram needs further assessment, the screening site can assign a provider for that follow-up. This is support for the abnormal result, not a promise of a permanent family doctor.

Questions to ask your provider

• Given my age and family history, how do the benefits and harms of screening balance for me?
• Do I meet OBSP criteria, and should I be assessed for the High Risk program?
• When was my last mammogram, and when would the next one be due?
• What should I do if I notice a change between screens?

Sources

• Breast screening recommendations and program eligibility — Ontario Health / Cancer Care Ontario
• Breast density and recall intervals — Ontario Health / Cancer Care Ontario
• Ontario Breast Screening Program — William Osler Health System
• High Risk OBSP eligibility and assessment — Ontario Health / Cancer Care Ontario
• Mammograms: what to expect — Ontario Health / Cancer Care Ontario

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