To achieve reductions in breast cancer mortality and morbidity, and to minimize the unwanted effects of screening, delivery of organized screening must be of high quality.
A standardized method of evaluation for all
Canadian breast screening programs has been repeatedly identified
as a necessity. With the CBCSD fully implemented, consistent
program data are available
for evaluation. In 1999, with this infrastructure in place, the
CBCSI's Quality Assurance Working Group, Database Technical
Subcommittee, and Database Management Subcommittee formed the
Evaluation Indicators Working Group (EIWG) to formalize a set of
performance measures and targets.
In February 2000, representatives of Health Canada and the breast screening evaluation community met at a national workshop as a first step towards developing a set of Canadian core indicators and targets for evaluating the performance and quality of organized breast screening programs. Ultimately, nine categories were selected:
Standardized methods of evaluation will promote the delivery of high-quality organized screening programs.
Using the nine categories as a guide, performance and quality indicators were gathered through a review of national documents from various countries, published research literature, Canadian federal documents and Canadian provincial/territorial screening program annual reports. The review focused on indicators that were currently available for breast cancer screening programs in publicly funded health care systems. With this review, the participants of the 2000 workshop identified 30 core performance and quality indicators, target outcomes for some of the indicators and recommendations on practical means to gather and report these data10. The EIWG then selected key indicators on the basis of outcomes, pragmatic considerations and efficiency. Subsequent meetings of the EIWG resulted in the following guidelines for reporting a key set of performance measures (Table 2)11. The 11 performance measures detailed here generally met the following criteria:
Monitoring screening programs requires reliable, standardized information that is comparable across provinces/territories. Some follow-up data must be obtained from external sources, which thereby complicates the evaluation process. Many, but not all, programs are directly linked to their provincial/territorial cancer registries in order to obtain cancer outcome data. Further complicating the evaluation process, some programs experience delays in obtaining registry data.
* No targets were set for in situ cancer detection rate, given the controversy surrounding the natural history of the condition.
Table 2
Performance measures and targets for breast cancer screening
programs in Canada
Indicator |
Definition |
Target |
1. Participation Rate |
Percentage of women who have a screening mammogram (calculated biennially) as a proportion of the eligible population. |
³ 70% of the eligible population (age
50-69) |
2.Retention Rate |
The estimated percentage of women who are re-screened within 30 months of their previous screen. |
³ 75% re-screened within 30 months (age
50-69) |
3.Abnormal Call Rate |
Percentage of women screened who are referred for further testing because of abnormalities found with a program screen. |
< 10% (initial screen) (age 50-69) |
4.Invasive Cancer |
Number of women detected with invasive cancer
during a screening episode per 1,000 women screened. |
> 5 per 1,000 (initial screen) |
5.In Situ Cancer Detection Rate |
Number of women detected with ductal carcinoma in situ (rather than invasive cancer) during a screening episode per 1,000 women screened. |
Surveillance and Monitoring Purposes
Only |
6.Diagnostic Interval |
Percentage of women who have completed the process from abnormal screen to resolution of abnormal screen, within 5 and 7 weeks of the screen date. |
³ 90% within 5 weeks if no open biopsy
(age 50-69) |
7.Positive Predictive Value |
Proportion of abnormal cases with completed follow-up found to have breast cancer (invasive or in situ) after diagnostic work-up. |
³ 5% (initial screen) (age 50-69) |
8.Benign to Malignant Open Biopsy Ratio |
Among open biopsies, the ratio of the number of benign cases to the number of malignant cancer cases. |
£ 2:1 open (initial & re-screen combined) (age 50-69) |
9.Invasive Cancer Tumour Size |
Percentage of invasive cancers with tumour size of £10 mm in greatest diameter as determined by the best available evidence: 1) pathological, 2)radiological, 3) clinical. |
> 25% £ 10 mm (age 50-69) |
10. Positive Lymph Nodes in Cases of Invasive Cancer |
Proportion of invasive cancers in which the cancer has invaded the lymph nodes. |
< 30% node positive (age 50-69) |
11. Post-screen Detected Invasive Cancer Rate |
Number of women with a diagnosis of invasive breast cancer after a negative screening episode per 10,000 person-years at risk, within 12 and 24 months of the screen date. |
< 6 per 10,000 person-years (within 0-12
months, age 50-69) |
Source: Health Canada. Report from the Evaluation Indicators Working Group: Guidelines for Monitoring Breast Cancer Screening Program Performance. Ottawa: Minister of Public Works and Government Services Canada, 2002.
Note: Table adapted from the Quality Determinants of Organized Breast Cancer Screening Programs Report.
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