A review of interval cancers previously assessed in a mammographic screening programme

A retrospective study was undertaken to identify cases where assessment had been performed at the site of the interval cancer. The study was performed for audit purposes and to identify potential learning points to improve assessment techniques. The interval cancers reviewed were from Breast Test Wales (South East) between April 1997 and April 2000.

Four hundred and three intervals were identified. This compares with 735 screen-detected cancers from the same time period (100,211 women screened in total). Eight (2%) had been previously assessed at the site of the interval cancer: five had been assessed for areas of microcalcification, two for asymmetric densities and one for distortion. From the microcalcifications only one had undergone cytological or histological examination.

The mean time between assessment and diagnosis of the cancer was 27 months. It was noted that in several of the cases there had been no change in appearance of the area that developed the interval in several contiguous screens and/or assessments.

We show examples of the cases, including case histories and mammograms.