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Ontario Breast Screening Program (OBSP)


The Ontario Breast Screening Program (OBSP) is a screening program that encourages people in Ontario to get screened for breast cancer. The OBSP screens 2 different groups of people who are eligible for breast cancer screening in Ontario: those at average risk and those at high risk.

Average Risk

The Ontario Breast Screening Program (OBSP) recommends that most eligible women, Two-Spirit, trans and nonbinary people ages 50 to 74 get screened with mammography every 2 years.

People ages 50 to 74 are eligible for screening through the OBSP if they:

  • have no new breast cancer symptoms
  • have no personal history of breast cancer
  • have not had a mastectomy
  • have not had a screening mammogram within the last 11 months
  • If transfeminine, have used feminizing hormones for at least 5 years in a row

People over age 74 can be screened within the OBSP; however, they are encouraged to make a personal decision about breast cancer screening in consultation with a primary care provider. The OBSP will not recall people over age 74 to participate in the program. To continue screening through the OBSP, a referral is required from a primary care provider.

High Risk

The Ontario Breast Screening Program (OBSP) recommends that people ages 30 to 69 who meet the High Risk OBSP eligibility criteria 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 OBSP does not accept new participants over age 70. However, when participants already in the High Risk OBSP turn 70, the program will continue to screen them with mammography only every year until they are age 74.

High Risk OBSP sites do not send letters to people over age 74 about participating in the program. To continue screening through the High Risk OBSP, a referral is required from a primary care provider.

For more information on eligibility for the High Risk Ontario Breast Screening Program, see Breast Cancer Screening for People at High Risk.

Benefits of an Organized Cancer Screening Program

  • Inviting people to participate in screening
  • Reminding screening participants when it is time for their next screening test
  • Telling participants their screening test results
  • Advising participants to follow up after an abnormal test result
  • Tracking participants throughout screening and diagnosis processes
  • Helping participants coordinate the next steps in their screening process if needed (e.g. genetic assessments for the High Risk Ontario Breast Screening Program)
  • Measuring program quality and performance

Benefits of Breast Cancer Screening

  • 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.
  • When breast cancer is found early, most people will survive for at least 5 years. However, if breast cancer is found later, only 3 out of 10 people will survive for at least 5 years.

Breast Cancer Screening Follow-up

Normal screening result

  • The Ontario Breast Screening Program directly notifies participants (with or without a primary care provider) of their normal results by mail. The letter will also tell participants when to get screened again.
  • The screening site also sends normal screening results to a screening participant’s primary care provider.

Abnormal screening result

  • Most people with abnormal mammograms do not have breast cancer. More tests are needed after an abnormal mammogram to determine whether a person has cancer.
  • Additional testing may include more mammography, breast ultrasound, breast magnetic resonance imaging and/or biopsies.
  • After a participant has an abnormal screening result, their screening site will notify their primary care provider and may help to schedule a timely follow-up appointment.
  • A participant with an abnormal mammogram who does not have a primary care provider will be assigned to a doctor or nurse practitioner by their screening site to follow them to diagnosis. If the participant does have breast cancer, they will be referred to a specialist for further care and management.