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Breast Cancer in Ontario

Breast cancer is the most commonly diagnosed cancer in Ontario, with 11,192 new cases of female breast cancer diagnosed in 2016. It is also the most commonly occurring cancer among First Nations females, with over 900 new cases diagnosed from 1991 to 2010. Modifiable risk factors for breast cancer include excess alcohol consumption and overweight or obesity.

Overall, Ontario’s cancer system as a whole is performing well with respect to breast cancer care when compared with other jurisdictions nationally and internationally. Ontario has the second-highest survival rate for breast cancer amongst all Canadian provinces. Survival rates for breast cancer are among the highest for all cancers diagnosed in Ontario, with rates continuing to increase. The 5-year relative survival ratio increased from 86% to 89% between 2002 and 2016. Relative survival is a ratio that compares the survival of people with cancer to the expected survival of people of the same age and sex in the general population.

The following highlights bright spots and opportunities, based on available indicators, to help focus efforts in improving the quality of care delivery for patients with breast cancer.

Diagnosis and Treatment

  • Women ages 50 to 74 have a lower risk of dying from breast cancer when they are screened regularly with mammograms. In 2017, 78% of women who needed a tissue biopsy were diagnosed within the recommended 7-week target of their abnormal screening mammogram result.
  • Participation rates for average risk breast cancer screening have remained steady at approximately 65%. Ontario’s screening participation compares favourably with rates in Australia and British Columbia, but rates are lower compared with rates in England. However, there may be differences in data definitions, methodologies and years reported. For detailed comparisons, see Breast Cancer Screening Participation.
  • Stage at diagnosis is one of the most important prognostic factors for cancer. More than 80% of staged breast cancer cases were diagnosed at stage 1 (44%) or stage 2 (39%) in 2017. In breast cancer, distributions of stage at diagnosis are similar between Ontario, Norway and Scotland. Patients tend to be diagnosed during earlier stages of the disease. When compared with Norway and Scotland, more Ontarians appear to be diagnosed at stage 1. For detailed comparisons, see Reporting of Cancer Stage at Diagnosis.
  • In general, the use of imaging for metastases is not recommended for early stage (stages 1 and 2) breast cancer patients with no symptoms of metastatic disease. This extra imaging does not improve patient care, and may delay treatment while the patient undergoes testing. In 2017, we continued to see steady declines in the percentages of stage 1 and 2 breast cancer patients undergoing imaging  for distant metastasis, suggesting appropriate breast cancer care
  • Typical treatment options for breast cancer include surgery, systemic drug therapy (chemotherapy), radiation therapy and other novel therapies developed through clinical trials. Treatment for breast cancer depends on the type of cancer, stage and patient choice.
  • Fourteen percent of patients visited the emergency department or were readmitted to hospital within 30 days after breast cancer surgery.  Looking at unplanned visits after cancer surgery helps us monitor complications and adverse events following cancer surgeries.


  • Recovering from cancer is different for each individual. People need access to the necessary healthcare services to help improve their quality of life after cancer treatment has ended.
  • Ongoing symptoms are common after cancer treatment. These may be related to the cancer or side effects of the treatment. Tracking symptoms over time helps clinicians identify changes that may be meaningful to patients and start conversations about symptom management. Electronic symptom screening can result in a greater focus on issues that are most important to the patient. In symptom screens completed by breast cancer patients in 2018:
    • 47% reported experiencing at least 1 moderate or severe symptom
    • approximately one-third included a moderate to severe level of tiredness during treatment or follow-up
    • 7% reported severe anxiety
    • 5% reported severe depression
  • Patients need appropriate follow-up care to detect cancer recurrence or new cancers. Among breast cancer patients who became survivors from 2012 to 2016, over 80% consistently received at least 1 mammogram in their first follow-up year. However, the proportion of breast cancer survivors having at least 1 mammogram in their first follow-up year is on the decline, from 84.7% among the 2012 survivor cohort to 82.5% among the 2016 survivor cohort.

For a visual summary of data on cancer burden and system performance for breast cancer across the cancer continuum, see Breast Cancer Overview.