A true screening environment for review of interval breast cancers: pilot study to reduce bias

To retrospectively assess the feasibility of an uninformed review process to evaluate interval breast cancers and to compare the number of false-negative cancers detected at uninformed review with the number detected at standard informed review.

Institutional review board approval was obtained for this retrospective study, and informed consent was waived. Mammograms showing interval cancer were included in the daily work of radiologists in a high-volume screening center. Each of three experienced radiologists read studies in the normal screening environment, without knowledge that identifiers had been changed to conceal the fact that studies were not current (ie, uninformed review). Results were compared with the standard review procedure, in which mammograms showing interval cancers were mixed with normal mammograms and read in a panel of 17-20 interval cancers per 80 normal studies by radiologists who were aware that they were participating in a review process (ie, informed review).

Of 21 interval cancers, six (29%) were interpreted as positive more often by the informed radiologists than by the uninformed radiologists. For 14 (67%) cancers, there was no difference in detection rate between the two groups, and one cancer (5%) was seen by one of the uninformed radiologists but by none of the informed radiologists. The screening environment review process was found to be feasible at the low volumes tested.

The number of false-negative cancers was higher in the informed review than in the uninformed review. This result suggests that bias exists with the informed review process.