IS THE 3-YEAR BREAST SCREENING INTERVAL TOO LONG - OCCURRENCE OF INTERVAL CANCERS IN NHS BREAST SCREENING PROGRAMS NORTH-WESTERN REGION

Objective-To report the detection rate of interval cancers in women sc reened by the NHS breast screening programme. Design-Detection of inte rval cancers by computer Linkage of records held by the screening cent res in the North Western Regional Health Authority with breast cancer registrations at the regional cancer registry. Setting-North Western R egional Health Authority. Subjects-137421 women screened between 1 Mar ch 1988 and 31 March 1992 who had a negative screening result. Results -297 invasive interval cancers were detected. The rate of detection of interval cancers expressed as a proportion of the underlying incidenc e was 31% in the first 12 months after screening, 52% between 12 and 2 4 months, and 82% between 24 and 36 months. Conclusion-The incidence o f interval cancers in the third year after breast screening approaches that which would have been expected in the absence of screening and s uggests that the three year interval between screens is too long.