Interval cancer rates in the Irish national breast screening programme

Abstract

Objective: To compare interval cancer rates from the Irish breast screening programme, BreastCheck, for the period 2000-2007 with those from other European countries.

Methods: Data from BreastCheck was linked to National Cancer Registry breast cancer registrations, to calculate numbers of women screened, screen-detected cancers, and interval cancers, by year of screening, in the first and second years after screening, and by initial or subsequent screen. Estimated underlying cancer incidence from the period 1996-1999 inclusive was used to calculate proportionate incidence. We calculated the interval cancer ratio as an alternative measure of the burden of interval cancers.

Results: There were 372,658 screening records for 178,147 women in the period 2000-2007. The overall interval rate was 9.6 per 10,000 screens. In the first year after screening, the interval cancer rate was 5.8 per 10,000 screens and this increased to 13.4 in the second year after screening. The screen detection rate for the period was 53.6 per 10,000 screened for all screens combined. Initial screens produced a higher detection rate at 66.9 per 10,000 screened compared with subsequent screens with a screen-detected rate of 41.4 per 10,000 screens.

Conclusion: Interval breast cancer rates for the first years of the programme are within acceptable limits and are comparable with those in other European programmes. Nationwide roll-out together with the adoption of digital mammography may have an impact on interval cancer rates in future years.

Keywords: Breast Cancer; Interval cancer; Screening.