||As of this Report
|PPV: Percentage of women, aged 50 to 74, with an abnormal OBSP screening mammogram result who were diagnosed with breast cancer (ductal carcinoma in situ or invasive) after diagnostic work-up
|Early return: Percentage of Ontario women, aged 50 to 72, screened in the OBSP with a biennial screening recall recommendation who had a subsequent program mammogram within 18 months of the previous mammogram
|Confirmed high risk by genetic assessment: Percentage of Ontario women, ages 30 to 69, referred to the OBSP who were confirmed to be at high risk for breast cancer by genetic assessment (counselling or testing)
|Screened within 90 days of confirmation of high risk status: Percentage of Ontario women aged 30 to 69 confirmed to be at high risk for breast cancer who were screened in the OBSP within 90 days of confirmation of high-risk status
| See Methodology and Approach to find out how the ratings are calculated.
Positive predictive value (PPV) is a quality measure that assesses the accuracy of breast cancer screening in detecting breast cancer (i.e. it is influenced by the abnormal call rate— the percentage of women referred for further testing due to an abnormal screening mammogram and cancer detection rates). In 2014, the PPV of breast cancer screening in the Ontario Breast Screening Program (OBSP) was 6%. A PPV of 6% means that in Ontario in 2014, approximately 50,000 women ages 50 to 74 had an abnormal OBSP screening mammogram, and 3,121 of those women were diagnosed with breast cancer.
Early return is an indicator of breast cancer screening participation behaviour that falls outside of the recommended guidelines for screening frequency. Approximately 15,000 Ontario women aged 50 to 72 who were screened through the OBSP in 2013 and who received a 2-year screening recall recommendation had a subsequent program mammogram within 18 months. Early return declined (improved) from 2010 (6%) to 2013 (4.6%), although there was considerable regional variation in 2013.
In 2014, approximately 7,000 women aged 30 to 69 who were referred to the OBSP High Risk Screening Program completed a genetic assessment (counselling or testing) to determine if they were at high risk for breast cancer. Of the women who completed an assessment, approximately 2,500 (or 34%) were determined to be at high risk. The proportion of women at high risk for breast cancer who were screened in the OBSP with mammography and magnetic resonance imaging (MRI) or ultrasound within 90 days of confirmation of their high-risk status was 56% in 2014, down from 73% in 2011–2012, the beginning of the high risk breast screening program.
What is breast cancer screening (mammogram)?
- 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 MRI uses magnetic waves and an intravenous contrast agent to create cross-sectional images of the breast2. Both tests can show changes in the breasts that may indicate 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 identified as being at high risk for breast cancer3.
In my words
Get it done. I think prevention is better than cure. Stay on top of it and if you feel anything, make sure you go to your doctor. You don’t want to be a hypochondriac or a worry wart, but it is so hard with these things that happen inside your body and you can’t tell what’s going on. So it’s better to go and find out rather than wait too long.
- Most women with an abnormal mammogram result will not have breast cancer4. More tests are required after an abnormal mammogram result to determine whether a 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 centres. For a map of locations, visit the section on Breast cancer screening participation.
What do the results show?
The PPV of breast screening in the OBSP has remained steady, and it varies by age group and among Local Health Integration Networks (LHINs) (Figures 1 and 2).
- The PPV of OBSP mammograms for Ontario overall in 2014 was 6%. Mammogram PPV has remained steady since 2011.
- In 2014, 3,121 of the nearly 50,000 Ontario women aged 50 to 74 who had an abnormal OBSP screening mammogram result went on to be diagnosed with breast cancer.
- There was some variation in mammogram PPV by LHIN. The LHINs with the highest PPV in 2014 were Erie St. Clair and Champlain (9%). Several LHINs had PPVs that were the same or close to the Ontario average of 6%.
- PPV increases with age. In 2014, the PPV of OBSP mammograms was highest in women aged 70 to 74 (11%) and lowest in women aged 50 to 54 (4%). A similar pattern can be seen in previous years.
- PPV is reported as a single measure for first and subsequent screens in order to be consistent with Ontario’s cervical and colorectal cancer screening programs. National breast screening guidelines have 2 separate PPV targets for first screens and subsequent screens (≥5% and ≥6%, respectively)5,6.
There is considerable regional variation in early return among LHINs (Figure 3).
- Early return declined from 6% for women screened in 2010 to 4.6% for women screened in 2013.
- Of the approximately 330,000 women aged 50 to 72 who were screened through the OBSP in 2013 and given a recommendation to re-screen in 24 months (2 years), approximately 15,000 (4.6%) had a subsequent program mammogram within only 18 months.
- The LHINs with the lowest (i.e. better) early return for women screened in 2013 were Hamilton Niagara Haldimand Brant and South East (both 1%). The LHINs that had the highest early return were Central and Toronto Central (both 9%).
- The percentage of women with biennial screening recommendations returning for a subsequent program mammogram within 18 months was lower in most LHINs for the cohort screened in 2013 than for the cohort of women screened in 2010 (i.e. it improved between 2010 and 2013). The LHIN with the greatest decrease in early return between 2010 and 2013 was Mississauga Halton (a decrease of 4 percentage points from 2010 to 2013).
- Early return will continue to provide direction for Cancer Care Ontario in its work with its regional partners to promote adherence to risk-appropriate screening intervals across the province.
Early return for breast cancer screening varies by socio-demographic factorⱡ.
- Early return varied by age group in 2013 (Figure 4). The percentage of women with a biennial screening recall recommendation returning for a subsequent program mammogram within only 18 months of a previous mammogram was lowest (4%) in the oldest age group (70 to 72 years old) and highest (5%) in the youngest age group (50 to 54 years old).
- Percentages of women returning for subsequent mammograms within 18 months of a previous mammogram (early return) were lower in rural-remote and rural-very remote areas (2%) than they were in urban areas (5%).
- Early return increased steadily as urban neighbourhood income quintiles rose, from 4% among women living in the lowest income urban areas to 6% among women living in the highest income urban areas.
- Early return was greatest among women living in neighbourhoods with the highest percentage of self-reported immigrant residents (7% for women screened in 2013). Early return was lowest among women living in neighbourhoods with the lowest percentage of self-reported immigrant residents (3%).
ⱡ Percentages by socio-demographic factor are available in the data tables (select the desired file type and click “Download”) and presented in the figures by age group.
The proportion of women referred for genetic assessment who are subsequently confirmed to be at high risk continues to increase, although there is some regional variation (Figure 5).
- The proportion of women referred to the OBSP High Risk Screening Program who were confirmed to be at high risk after referral increased to 34% in 2014 (from 31% in 2013 and 29% in 2011–2012).
- There is some regional variation for this indicator. In 2014, the LHIN with the highest percentage of women confirmed to be at high risk for breast cancer after genetic assessment was Mississauga Halton (47%). The LHINs with the lowest percentage of women confirmed to be at high risk for breast cancer after genetic assessment were Erie St. Clair and North West (26%).
- The OBSP has set a provincial target of 30% or greater for this indicator, meaning that approximately 1 in 3 women who are referred for genetic assessment are confirmed to be at high risk for breast cancer.
- Monitoring this indicator allows Cancer Care Ontario to see if the high-risk referral criteria are interpreted correctly by primary care providers, and to ensure that the criteria identify women who may be at increased risk for breast cancer.
The proportion of women confirmed to be at high risk who are screened in the OBSP within 90 days of confirmation of high-risk status has decreased since the start of the OBSP High Risk Screening Program, and there is considerable regional variation (Figure 6).
- In 2011–2012, at the start of the OBSP High Risk Screening Program, 73% of women confirmed to be at high risk for breast cancer were screened by a mammogram and MRI or ultrasound within 90 days of confirmation of their high-risk status, compared to 56% in 2014.
- The OBSP has set a provincial target of 90% or greater for this indicator, meaning that about 9 in 10 women should be screened within 90 days of confirmation of high-risk status.
- There was considerable regional variation for this indicator. In 2014, the LHIN with the highest percentage of women screened within 90 days of confirmation of their high-risk status was Champlain (82%). The LHIN with the lowest percentage of women screened within 90 days was Mississauga Halton (30%).
- The decrease in women screened within the 90-day guideline may be partly attributed to increasing wait times for MRIs. Current wait times are available on the Ontario Wait Times website.
Why is this important to Ontarians?
Mammography is important for the early detection of breast cancer, but it is not perfect.
- Finding breast cancer early increases the number of treatment options available, and it can lead to better treatment outcomes and survival rates7.
- 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 698.
- Women without breast cancer who receive abnormal mammogram results (false-positives) may unnecessarily undergo additional imaging and biopsies. The likelihood of a false-positive result is lower for re-screens than for initial screens because previous mammograms can be used for comparison9.
- Even with a mammogram, some breast cancers are not detected (false-negatives). Dense breast tissue and current use of hormone replacement therapy are associated with an increased risk of breast cancer being missed by screening10.
- The PPV of a screening test is dependent on the underlying prevalence of disease in the population being screened. This may help to explain the variation observed across LHINs and age groups.
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 and MRI or ultrasound.
- Communication to women and healthcare providers includes the following:
- women eligible for screening through the OBSP average risk program are sent invitations to be screened through the program, along with information about breast cancer screening and details on how to find an OBSP centre.
- normal result letters are sent to women after their screening visits.
- women screened in the OBSP are sent recall and reminder letters when they are due for their next round of screening.
- OBSP centres follow up on abnormal screening results and communicate normal and abnormal results to a woman’s healthcare provider.
- Coordination and navigation includes the following:
- arranging genetic assessment (if appropriate) for women who have been referred to the OBSP High Risk Screening Program;
- booking mammography and breast MRI (or, if appropriate, screening ultrasound) appointments via OBSP centres;
- suggesting an appropriate screening recall interval based on a woman’s screening result and risk factors; and
- having OBSP assessment centres coordinate follow-up tests, track test results and provide navigation from abnormal screen to final diagnosis for women with abnormal screening results.
The OBSP is continually evaluated and improved to maximize benefits and minimize limitations.
- Women are encouraged to get screened through the OBSP. As an organized screening program, it offers important benefits, such as inviting women to participate in screening, reminding participants when it is time for their next screening test, notifying participants of screening results, tracking participants throughout screening processes and evaluating program quality and performance.
- A robust quality assurance and performance monitoring framework is in place for the OBSP.
- All OBSP screening centres are accredited by the Canadian Association of Radiologists (CAR) Mammography Accreditation Program (MAP). The CAR MAP guidelines cover radiologist and medical radiation technologist (MRT) qualifications, equipment, quality control, quality assurance, image quality and radiation dose11.
- Feedback on performance, which is then compared to national targets and quality standards, is provided annually to all OBSP screening and assessment centres, and to individual radiologists.
- The OBSP conducts regular physical inspections of mammography equipment at OBSP centres.
- The OBSP’s quality assurance program will continue to provide performance feedback to individual OBSP centres, radiologists and MRTs, as well as identify opportunities for improvement (where necessary).
- Cancer Care Ontario [Internet]. Toronto: Cancer Care Ontario. Mammograms; 2015 Jan 16 [cited 2015 Dec 17]. Available from: https://cancercare.on.ca/pcs/screening/breastscreening/mammograms.
- The Canadian Cancer Society [Internet]. Toronto: Canadian Cancer Society; c2016. Magnetic Resonance Imaging (MRI); [cited 2016 Jan 29]. Available from: http://www.cancer.ca/en/cancer-information/diagnosis-and-treatment/tests-and-procedures/magnetic-resonance-imaging-mri/?region=on.
- Chiarelli AM, Prummel MV, Muradali D, Majpruz V, Horgan M, Carroll JC, et al. Effectiveness of screening with annual magnetic resonance imaging and mammography: results of the initial screening from Ontario high risk breast screening. J Clin Oncol. 2014 Jul 20; 32(21):2224–30.
- Cancer Care Ontario. Ontario Breast Screening Program 2011 report. Toronto: Cancer Care Ontario; 2013.
- Canadian Partnership Against Cancer. Report from the evaluation indicators working group: guidelines for monitoring breast cancer screening program performance. 3rd Edition. Toronto: Canadian Partnership Against Cancer; 2013.
- Canadian Partnership Against Cancer. Breast cancer screening in Canada: monitoring and evaluation of quality indicators—results report. Toronto: Canadian Partnership Against Cancer; 2013.
- Nelson H, Tyne K, Naik A, Bougatsos C, Chan B, Humphrey L. Screening for breast cancer: an update for the U.S. Preventive Services Task Force. Ann Intern Med. 2009 Nov 17; 151(10):727–37.
- 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 ages 40–74 years. CMAJ. 2011 Nov 22; 183(17):1991–2001.
- Chiarelli AM, Halapy E, Nadalin V, Shumak R, O’Malley F, Mai V. Performance measures from 10 years of breast screening in the Ontario Breast Screening Program, 1990/91 to 2000. Eur J Cancer Prev. 2006 Feb; 15(1):34–42.
- Chiarelli AM, Kirsh VA, Klar NS, Shumak R, Jong R, Fishell E, et al. Influence of patterns of hormone replacement therapy use and mammographic density on breast cancer detection. Cancer Epidemiol Biomarkers Prev. 2006 Oct; 15(10):1856–62.
- The Canadian Association of Radiologists [Internet]. Ottawa: the Canadian Association of Radiologists; c2009. Mammography accreditation program (MAP); [cited 2015 Dec 17]. Available from: http://www.car.ca/en/accreditation/map.aspx.