Breast Cancer Screening Participation and Retention
Measure: Participation: age-adjusted percentage of Ontario screen-eligible women, age 50 to 74, who completed at least 1 mammogram within a 30-month period
As of this Report:
Of the over 2 million Ontario women age 50 to 74 who were eligible for breast cancer screening for the 30-month period of 2015 to 2016 (2015–2016), more than 1.3 million were screened with a mammogram. Participation in average risk breast cancer screening has remained steady at around 65% since the 2009–2010 period.
The percentage of women age 50 to 74 who are screened through the Ontario Breast Screening Program (OBSP), Ontario’s population-based breast cancer screening program, continues to increase. Of all eligible women screened for breast cancer in 2015–2016, 85% were screened through the program, compared to 70% for 2009–2010.
Most women age 50 to 74 should be screened every 2 years with mammography. Women age 30 to 69 who are confirmed to be at high risk of getting breast cancer should be screened once a year with a mammogram and breast magnetic resonance imaging (MRI) (or screening breast ultrasound if MRI is not medically appropriate).
Among Ontario women age 50 to 72 who had a mammogram through the OBSP, the percentage of women returning within 30 months for another mammogram has decreased in each cohort of women screened since 2011. In 2014, 79% of women returned to screening, compared to 83% in 2011. This trend of decreasing retention is also seen among Ontario women age 30 to 68 who were screened through the High Risk OBSP and returned within 15 months for another MRI or ultrasound. In 2015, 70% of women returned for screening through the High Risk OBSP, compared to 82% in 2012.
What is breast cancer screening?
- Cancer screening is testing for people who may be at risk of getting cancer, but who have no symptoms and generally feel fine. It is not meant to diagnose cancer. Instead, it helps determine which people are more likely to develop cancer in the future. Ontario operates screening programs for 3 types of cancer: breast, cervical and colorectal.
- The purpose of breast cancer screening is to find cancer at an early stage, when it may be smaller and easier to treat.
- A mammogram uses low-dose X-rays to produce images of the breast . A breast MRI uses radio waves and a magnetic field to create cross-sectional images of the breast and an intravenous contrast agent (e.g., dye) is used most of the time . Both tests can find breast cancers when they are small, less likely to have spread and more likely to be treated successfully.
- Breast cancer screening with mammography is recommended every 2 years for most women age 50 to 74 .
- Breast cancer screening with mammography and breast MRI (or screening breast ultrasound if MRI is not medically appropriate) is recommended every year for women age 30 to 69 who are identified as being at high risk for breast cancer .
- Most women with an abnormal mammogram result will not have breast cancer . More tests are needed after an abnormal mammogram result to determine whether cancer is present.
- Diagnostic assessment includes additional radiological or surgical procedures, such as diagnostic mammography, ultrasonography, and core and/or open surgical biopsy.
- In Ontario, breast cancer screening occurs through both OBSP and non-OBSP sites.
What do the results show?
Although breast cancer screening participation (the percentage of eligible women who received a mammogram) has levelled off, more Ontario women are being screened through the Ontario Breast Screening Program.
- Provincial breast cancer screening participation has remained steady at 65% since the period of 2008–2009.
- About 1.35 million Ontario women age 50 to 74 were screened for breast cancer during the 2015–2016 period, and over 1 million of these women were screened through the OBSP (85% of all mammograms performed in Ontario during that time).
Breast cancer screening participation varies across the province (Figure 2).
- Over the period from 2015 to 2016 (2015-2016), the Local Health Integration Network (LHIN) with the greatest participation was North Simcoe Muskoka (69%). The LHIN with the lowest breast cancer screening participation was North West (61%).
- The Central West LHIN showed the greatest improvement in participation from the period of 2009–2010 to 2015–2016 (up 2 percentage points). Over that same time, participation decreased by 6 percentage points in the North West LHIN.
Breast cancer screening participation varies by age group (Figure 3).
- For the 2015–2016 period, participation was highest in women age 65 to 69 (69%) and lowest in women age 70 to 74 (59%). A similar pattern can be seen in previous years.
Retention in the Ontario Breast Screening Program has decreased (Figure 4).
Measure: Retention: percentage of Ontario screen-eligible women, age 50 to 72, who had a subsequent OBSP screening mammogram within 30 months of a previous program mammogram
As of this Report:
- Approximately 433,000 women age 50 to 72 who had an OBSP mammogram in 2014 returned for a subsequent program mammogram within 30 months (79%).
- The LHIN with the highest retention for women screened in 2014 was Erie St. Clair (85%). North West had the lowest retention at 70%.
- Retention in the OBSP has decreased in each cohort of women screened since 2011. Analysis showed no differences in subgroups of women who returned for annual vs. biennial screening (data not shown).
- The greatest difference in OBSP screening retention was observed in the North West LHIN, which experienced a 10 percentage point decrease between 2013 (80%) and 2014 (70%).
- The OBSP sends recall letters to most women about 24 months after their previous program mammogram, which is consistent with Cancer Care Ontario’s screening guidelines . The retention indicator allows for a 6-month grace period to account for potential wait times for screening mammogram appointments at OBSP sites.
- Initial re-screens (returning after a first mammogram) and subsequent re-screens (returning for further mammograms) are being reported as a single measure of retention to be consistent with Ontario’s cervical and colorectal cancer screening programs.
- National breast cancer screening guidelines have separate targets for initial and subsequent program re-screens: ≥75% for initial re-screens within 30 months and ≥90% for subsequent re-screens within 30 months .
Retention in the Ontario Breast Screening Program varies by age group (Figure 5).
- Among women who had an OBSP mammogram in 2014, retention was highest in those age 65 to 69 (82%) and lowest in those age 50 to 54 (74%). A similar pattern can be seen in previous years.
Retention in the High Risk Ontario Breast Screening Program varies by region (Figure 6).
Measure: High Risk OBSP retention: percentage of Ontario women, age 30 to 68, with an abnormal high risk screen (MRI or ultrasound), who had a subsequent OBSP high risk screen within 15 months
As of this Report:
- Overall, retention in the High Risk OBSP has decreased in Ontario. Approximately 70% women who had a High Risk OBSP MRI or ultrasound in 2015 returned for a subsequent program MRI or ultrasound within 15 months. Screening wait times in the High Risk OBSP may have contributed to this decrease, specifically for breast MRI.
- The LHIN with the highest retention for the High Risk OBSP in 2015 was Waterloo Wellington (87%). The Mississauga Halton LHIN had the lowest retention at 46%.
- The LHIN with the most improvement in retention for the High Risk OBSP was the North West LHIN, which showed a 22 percentage point increase from 2014 (47%) to 2015 (69%). The Champlain LHIN experienced a 23 percentage point decrease in retention, down from 79% in 2014 to 56% in 2015.
- National breast cancer screening guidelines have no targets for High Risk OBSP retention .
Retention in the High Risk Ontario Breast Screening Program varies by age group (Figure 7).
- Among women who had a High Risk OBSP MRI or ultrasound in 2015, retention was highest in those age 60 to 68 (81%) and lowest in those age 30 to 39 (60%). A similar pattern can be seen in previous years.
Why is this important to Ontarians?
Breast cancer burden is high in Ontario.
- Breast cancer is the most common cancer diagnosed in Ontario women, and it is ranked as the third most common cause of cancer mortality (i.e., deaths) .
- It is estimated that 11,762 Ontario women will be diagnosed with breast cancer in 2018 and approximately 1,977 women will die of the disease .
- Women over age 50 are at the greatest risk of getting breast cancer, with 61% of breast cancers in Ontario in 2016 having been diagnosed in women age 50 to 74 . Regular screening plays an important role in improved outcomes.
- Evidence indicates that using mammography to screen for breast cancer resulted in a 21% reduction in breast cancer mortality in average risk women age 50 to 69 (compared to no screening) .
- Finding breast cancer early can increase the available treatment options, and it can lead to better treatment outcomes and survival [7, 8].
- In studies that demonstrated the benefit of regular breast cancer screening, participants returned within recommended intervals [9–11].
Organized screening offers several important benefits to women and their healthcare providers.
- The OBSP and High Risk OBSP provide high-quality screening for most women through the use of mammography, and through mammography and MRI for women at high risk (or screening breast ultrasound if MRI is not medically appropriate).
- Quality assurance is ensured through the accreditation of all OBSP sites by the Mammography Accreditation Program of the Canadian Association of Radiologists.
- Communication with women and healthcare providers includes the following:
- Women eligible for screening through the OBSP are sent invitations to get screened, along with information about breast cancer screening and details on how to find an OBSP site.
- After their screening appointment, women with normal screening results get letters telling them their results are normal.
- Women screened through the OBSP get letters reminding them when to get screened again.
- OBSP sites follow up on abnormal screening results and send normal and abnormal results to a woman’s healthcare provider.
- Coordination and navigation include the following:
- High Risk OBSP sites arrange genetic assessment (if appropriate) for women referred to the program.
- High Risk OBSP sites book screening mammography and screening breast MRI (or screening breast ultrasound if MRI is not medically appropriate).
- The OBSP indicates whether a woman should be screened in 1 year or 2 years based on her screening results and risk factors.
- OBSP assessment sites help guide women with abnormal screening results through to diagnosis by coordinating follow-up tests and documenting the results of those tests.
How does Ontario compare with other jurisdictions?
- Ensuring that the data and measures from other jurisdictions are comparable to those used by Ontario is a challenge. Caution should be used when comparing Ontario’s indicator results to those from other jurisdictions due to potential differences in data definitions, methodologies and time periods. Cross-jurisdictional comparison is still useful, however, for providing a rough indication of how well Ontario is doing compared to other jurisdictions.
- Ontario compares favourably to Australia in screening participation. For the period of 2015–2016, Ontario’s breast cancer screening participation was 64.8%, compared to 54.4% in Australia. However, Australia’s participation indicator captures a 24-month period, while Ontario’s indicator captures a 30-month period .
- For more information on comparisons of breast cancer screening participation among jurisdictions, see the Cancer Screening Quality Index’s (CSQI’s) jurisdictional comparison section.
- The OBSP will be expanding as non-OBSP screening sites transition into the program. Screening through an organized program such as the OBSP offers important benefits to women and healthcare providers, including communicating normal and abnormal test results to a woman’s healthcare provider, coordinating follow-up tests when appropriate, and helping women with abnormal screening results navigate from abnormal screen to final diagnosis.
- Cancer Care Ontario has developed an online Primary Care Screening Activity Report (PC SAR) for all 3 screening programs (breast, cervical and colorectal cancer). This tool, which is accessed online, allows physicians in a patient enrolment model practice to see the complete screening status of each of their enrolled age-eligible patients, including those who are due for screening and follow-up.
- Cancer Care Ontario continues to work with the Ministry of Health and Long-Term Care to identify ways to further support the High Risk OBSP so that Ontario women can continue to benefit from the program.