Breast Cancer Screening Participation

Key findings

In 2014–2015, of the over 2 million Ontario women aged 50 to 74 eligible for breast cancer screening, about 1.3 million were screened with a mammogram. Participation in breast screening has remained steady at around 65% since 2008–2009.

The percentage of women screened specifically through the Ontario Breast Screening Program (OBSP) continues to increase, with 82% of all eligible women having been screened for breast cancer through the program in 2014–2015.

The number of women who meet eligibility criteria for OBSP screening also continues to increase and is up by approximately 400,000 women since 2008–2009.

Among Ontario women who had a mammogram through the OBSP in 2013, 81% returned within 30 months for another mammogram, which is a decrease from the 83% who returned in 2012.

Measure	Desired Direction	As of this Report
Participation: Age-adjusted percentage of Ontario screen-eligible women, aged 50 to 74, who completed at least 1 mammogram within a 30-month period
Retention: Percentage of Ontario screen-eligible women, aged 50 to 72, who had a subsequent OBSP screening mammogram within 30 months of a previous program mammogram
See Methodology and Approach to find out how the ratings are calculated.

What is breast cancer screening?

• A screening test identifies people in a healthy, asymptomatic population who may be at risk for disease. It is not a diagnostic test. The purpose of breast screening is to find cancer at an early stage, when it is easier to treat. Ontario operates screening programs for 3 types of cancer: breast, cervical and colorectal.
• A mammogram uses low-dose X-rays to produce images of the breast¹. A breast magnetic resonance imaging (MRI) scan uses magnetic waves and an intravenous contrast agent to create cross-sectional images of the breast¹. Both tests can show changes in the breasts that may be early signs of breast cancer, even when the changes are too small for a woman or her doctor to feel or see.
• Breast cancer screening with mammography is recommended every 2 years for average risk women aged 50 to 74¹.
• Breast cancer screening with mammography and breast MRI is recommended every year for women aged 30 to 69 who are identified as being at high risk for breast cancer¹.
• Most women with an abnormal mammogram result will not have breast cancer¹. 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 the OBSP (an organized province-wide screening program) and through non-OBSP sites.

What do the results show?

Although screening participation (percentage of eligible women who received a mammogram) has levelled off, more Ontario women are being screened through the OBSP and the number of women in Ontario eligible for breast cancer screening has increased substantially (Figures 2 and 3).

• Provincial breast cancer screening participation has remained steady at 65% since 2008–2009. About 1.3 million Ontario women aged 50 to 74 were screened for breast cancer in 2014–2015. Of the women who were screened for breast cancer in 2014–2015, over 1 million were screened in the OBSP (82% of all mammograms performed in Ontario during 2014–2015).
• The number of women who meet eligibility criteria for OBSP screening also continues to increase and is up by approximately 400,000 women since 2008–2009.

Breast cancer screening participation varies across the province (Figure 3).

• In 2014–2015, the Local Health Integration Network (LHIN) with the greatest participation was North Simcoe Muskoka (69%). The LHINs with the lowest breast cancer screening participation were Central West, Toronto Central and North West (62% for all).
• The Central West LHIN showed the greatest improvement in participation from 2008–2009 to 2014–2015 (up 3 percentage points). Participation decreased by 4 percentage points in the North West LHIN during the same time period.

Breast cancer screening participation varies by age group (Figure 4).

Breast cancer screening participation varied by age group. In 2014–2015, participation was highest in women aged 65 to 69 (69%) and lowest in women aged 70 to 74 (59%). A similar pattern can be seen in previous years.

Retention in the OBSP has decreased (Figure 5).

• The OBSP sends recall letters to women about 24 months after their previous program mammogram, which is consistent with Cancer Care Ontario screening guidelines¹. The retention indicator allows for a 6-month grace period to account for potential wait times for screening mammogram appointments at OBSP sites.
• Approximately 412,000 women who had an OBSP mammogram in 2013 returned for a subsequent program mammogram within 30 months (81%). Breast screening retention has decreased in each cohort of women screened since 2010.
• 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 screening guidelines have 2 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 months².
• The LHIN with the highest retention for women screened in 2013 was Erie St. Clair (87%). Central West had the lowest retention at 77%.

Retention in the OBSP varies by age group (Figure 6).

• Among women who had an OBSP mammogram in 2013, retention was highest in those aged 65 to 69 (84%) and lowest in those aged 50 to 54 (77%). 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 second-most common cause of cancer mortality (i.e. deaths)³.
• In 2016, it is estimated that 9,900 Ontario women were diagnosed with breast cancer and approximately 1,850 women died of the disease³.
• Women over age 50 are at the greatest risk of getting breast cancer, with 82% of breast cancers in Canada having been diagnosed in women 50 and over in 2015³. Regular screening plays an important role in improved outcomes.
• A recent summary of evidence reported that using mammography to screen for breast cancer resulted in a 21% reduction in breast cancer mortality in average-risk women aged 50 to 69, compared to no screening⁴.
• Finding breast cancer early can increase the treatment options available, and can lead to better treatment outcomes and survival^4,5.
• In studies that demonstrated the benefit of regular breast cancer screening, participants returned within recommended intervals^6–8.

Organized screening offers important advantages for women and physicians.

• The OBSP provides high-quality screening for women at average risk of developing breast cancer through the use of mammography, and for women at high risk through mammography, plus MRI or ultrasound.
• Communication to women and health care providers includes:
  • women eligible for screening through the OBSP are sent invitations to get screened, along with information about breast cancer screening and how to find an OBSP site;
  • normal result letters are sent to women after their screening visits;
  • women screened through the OBSP are sent recall and reminder letters when they are due for their next round of screening; and
  • OBSP sites follow up on abnormal screening results, and communicate normal and abnormal results to a woman’s health care provider.
• Coordination and navigation includes:
  • arranging genetic assessment (if appropriate) for women who have been referred to the High Risk OBSP;
  • booking mammography and breast MRI (or, if appropriate, screening ultrasound) appointments via OBSP sites;
  • suggesting an appropriate screening recall interval based on a woman’s screening result and risk factors; and
  • having OBSP assessment sites coordinate follow-up tests, track test results and provide navigation from abnormal screen to final diagnosis for women with abnormal screening results.

How does Ontario compare with other jurisdictions?

• Ensuring that the data and measures from other jurisdictions are comparable to Ontario’s 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 other provinces in self-reported screening participation. In 2012, 73% of Ontario women aged 50 to 69 reported having had a mammogram for any reason in the past 2 years. Ontario had the second-highest self-reported participation, behind Quebec (74%)*⁹.
• For more information on comparisons of breast cancer screening participation among jurisdictions, see CSQI’s jurisdictional comparison section.

*Note: All provincial comparisons were based on women aged 50 to 69. Some provinces only monitor participation in screening programs and cannot directly be compared.

Next steps

• The OBSP will be expanding as non-OBSP screening sites are transitioned into the program. Screening through the OBSP offers important benefits to women and physicians, including communicating normal and abnormal test results to a woman’s health care 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 (cervical, breast and colorectal cancer). This tool (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. Next steps include working with the Regional Primary Care Leads to identify barriers to adoption of the tool, and to promote and encourage use of the PC SAR.

View Notes

1. Cancer Care Ontario. Ontario Cancer Screening Performance Report 2016. Toronto: Cancer Care Ontario; 2016.
2. Canadian Partnership Against Cancer. Breast Cancer Screening in Canada: Monitoring and Evaluation of Quality Indicators- Results Report, January 2009–December 2010. Toronto: Canadian Partnership Against Cancer; 2015.
3. Canadian Cancer Society’s Advisory Committee on Cancer Statistics. Canadian Cancer Statistics 2016. Toronto, ON: Canadian Cancer Society; 2016.
4. Canadian Task Force on Preventive Health Care, Tonelli M, Gorber CS, Joffres M, Dickinson J, Singh H, et al. Recommendations on screening for breast cancer in average-risk women aged 40–74 years. CMAJ. 2011 Nov 22; 183(17):1991–2001.
5. Nelson HD, Fu R, Cantor A, Pappas M, Daeges M, Humphrey L. Effectiveness of breast cancer screening: systematic review and meta-analysis to update the 2009 U.S. Preventive Services Task Force Recommendations. Ann Intern Med. 2016 Feb 16; 164(4):1–20.
6. Nystrom L, Andersson I, Bjurstam N, Frisell J, Nordenskjold B, Rutqvist LE. Long-term effects of mammography screening: updated overview of the Swedish randomised trials. The Lancet. 2002 Mar 16; 359(9310):909–19.
7. Otto SJ, Fracheboud J, Looman CW, Broeders MJ, Boer R, Hendriks JH, et al. Initiation of population-based mammography screening in Dutch municipalities and effect on breast-cancer mortality: a systematic review. The Lancet. 2003 Apr 26; 361(9367):1411–7.
8. United States Preventive Services Task Force. Screening for breast cancer: recommendations and rationale. Ann Intern Med. 2002 Sep 3; 137(5 Part 1):344–6.
9. Canadian Partnership Against Cancer. The 2016 cancer system performance report. Toronto: Canadian Partnership Against Cancer; 2016.