The incidence of interval breast cancers from Wirral Breast Screening Unit between 1 January 1994 and 30 June 2000

Objective

To report the detection rate of interval breast cancers in the Wirral Breast Screening Unit between 1 January 1994 and 30 June 2000.

Methods

Women aged 50–64 years were invited for screening, and data prospectively collected for both screen-detected and interval cancer detection rates. Case notes for interval cancers were reviewed together with two-view mammography. True interval and false negative rates were determined for the interval cancers. Rates of recurrence and survival times for these cancers were also collected.

Results

Between 1 January 1994 and 30 June 2000, 82,510 women were invited to attend for screening at the Wirral Breast Screening Unit. A total 63,159 (77%) women attended and 293 screen-detected cancers were observed. A total of 215 invasive interval cancers were detected for the same period, 28% of these occurred in the first 12 month interval, 37% in the next 13–24 months and 36% in the last 25–36 month interval.

Conclusions

The rate of interval cancers was similar over the 3-year period between screening rounds and the incidence of these cancers may not be reduced by shortening the mammographic screening period.