Post-screen cancer detection rate

Why is it important? This indicator provides insight into the sensitivity of mammography screening and the sustainability of screening activities and efforts. Post-screen cancers are cancers detected during the screening interval, i.e. between regular mammography screening and before the next screening appointment. This can include cancers that were missed during screening and new cancers that developed during the screening interval. Having a low post-screen cancer rate is ideal if screening programs are to be successful in achieving the expected reduction in breast cancer mortality.

Indicator definition: The number of breast cancers (DCIS and invasive) found after a normal or benign (non-cancerous) breast cancer screening episode per 10,000 screens.

Target: No target

Measurement timeframe: The screening years January 1, 2017, to December 31, 2018 is used for this indicator to allow for time for follow-up and diagnosis.

Indicator calculation:

  • Numerator: The number of invasive breast cancers or DCIS detected within each of the follow-up intervals (0 to 12 months, >12 to 24 months and >24 to 36 months).
  • Denominator: The number of screening mammograms with normal or benign results within the measurement timeframe.

Additional considerations: The interpretation of this indicator is influenced by factors such as the abnormal call rate, the recommended screening interval, the underlying incidence rate, age, opportunistic screening, and the diagnostic interval.

Post-screen diagnosed breast cancer rate (per 10,000 screens) among individuals aged 50-74 who were screened within a screening mammography program, by jurisdiction — screening year 2017-18

MB, NB, PE: Data for DCIS and invasive breast cancer were combined to avoid residual disclosures of small numbers.
Data table and footnotes

The post-screen breast cancer rate for DCIS and invasive cancers were combined for Manitoba, New Brunswick, and Prince Edward Island, but not for British Columbia and Ontario.

In Manitoba, New Brunswick, and Prince Edward Island, the highest post-screen cancer detection rate was observed within the >12 months-24 months follow-up interval, ranging from 8.2 per 10,000 screens to 11.5 per 10,000 screens.

In both British Columbia and Ontario, the rate of post-screen invasive cancers was higher than the rate of post-screen DCIS cancers in all follow-up intervals. The rate of post-screen invasive cancers in British Columbia and Ontario for the >12 months-24 months follow-up interval was 8.3 per 10,000 screens and 8.6 per 10,000 screens respectively.