Interval cancers are cancers that are diagnosed during the interval between a negative screen and the subsequent screen. The rate of interval cancers is a performance indicator in the terms of reference of the Quebec Breast Cancer Screening Program (PQDCS). The PQDCS terms of reference do not set a standard for interval cancer rates, but the Evaluation Indicators Working Group, which monitors breast cancer screening programs in Canada, has determined that the rate of interval cancers should not exceed 6 cases of invasive cancer per 10,000 person-years within 12 months of a negative screen, or 12 cases per 10,000 person-years within 24 months of a negative screen.
The primary objective of this analysis was to estimate the rate of interval cancers among women who received an...