Report from the Evaluation Indicators Working Group: Guidelines for Monitoring Breast Screening Program Performance

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Future Directions

The development of a set of performance measures for organized breast cancer screening programs must be an ongoing process. The body of research pertaining to organized breast cancer screening is constantly evolving, as is the technology and methodology used to screen, diagnose and treat the disease. The quality of evidence used to support the use of performance measures presented in this document varies greatly from measure to measure and is subject to change with the continual introduction of new research evidence. The data used in the calculation of these measures, and possible future measures, are still maturing in terms of quality and timely availability. Consequently, it is a challenge to establish comprehensive, long-term evaluation plans with valid, reliable performance measures. As a result, a multiphase strategic plan has been proposed with the release of these guidelines.

Phase 1: Monitoring Proposed Performance Measures (Years 1 and 2)

The first formal use of these measures will be in subsequent releases of the biennial report on Organized Breast Cancer Screening Programs in Canada8. In 2 years' time, a subsequent strategic working group will be formed to examine the outcomes of these monitoring efforts. At that time, the group will reassess the 11 measures in terms of progress made towards achieving the national targets. Targets will be adjusted or redefined by consensus supported by new research or expert opinion. Changes to the definitions of the measures and methods of calculation will also be considered on the same basis. Several measures have already been slated for special review for a number of reasons, as follows.

Performance Measures Under Review

In situ cancer detection rate: While ductal carcinoma in situ (DCIS) is widely accepted as an obligate precursor of invasive disease, the time frame in which this occurs is not firmly established. The potential for cases of DCIS to remain asymptomatic throughout the individual's natural lifespan suggests a potential for overdiagnosis with its attending negative consequences. The Working Group will continue to monitor in situ cancer detection rates and will consider defining a target under the appropriate circumstances.

Benign to malignant open biopsy ratio: The precision of this measure needs to be considered in light of the small numbers of cases involved. Therefore it is recommended that open biopsy yield ratios be presented with confidence intervals. These ratios need to be observed over time to assess trend stability and thus the appropriateness of the specified target.

Positive lymph nodes in cases of invasive cancer: In cases of invasive cancer, involvement of the lymph nodes can be difficult to establish. Data for this indicator may therefore be unreliable. New diagnostic techniques (e.g., sentinel node biopsy) are likely to have an impact on this indicator.

Performance by screening modality: Screening modality (mammography alone; mammography and/or CBE) has an impact on program performance, as indicated in the Status sections of the preceding measures. Separate targets will be established by consensus, supported by new research or expert opinion, for each screening modality.

Phase 2: Revisiting Other Performance Measures (Years 3 and 4)

While the best possible assessment of the morbidity and mortality reducing potential of breast cancer screening was the foremost priority in the selection of these measures, the timely availability of high quality data was also an influential factor. Meaningful targets, useful for national comparison through frequent monitoring, were also requisite. These criteria do not, however, fully cover the range of performance measures needed to establish comprehensive long-term evaluation plans. From that perspective, factors such as equitable access, representative participation, acceptability of services to clients, cost minimalization, and program promotion must be assessed. In recognition of the need for a more complete inventory of indicators for use in future evaluation initiatives, a working group will be formed again, after 2 years, to reconsider the feasibility of adding new measures or including measures previously explored (but not published) to a second edition of this document. Previously explored measures with the potential for future use are outlined in Table 2.

Phase 3: Ongoing Evaluation (Year 5)

Having completed phases 1 and 2 of the evaluation indicators strategic plan, the working group will consider the need to continue the process of revisiting this collection of performance measures. A plan will be formed reflecting the contemporary state of breast cancer research and the performance measurement needs of organized screening programs in Canada. This plan will detail the future scope of the working group's activities.

Table 2: Possible Canadian Breast Cancer Screening Measures for Future Use

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