Interval Breast Cancer: What a 6.5-Million–Mammogram Study Teaches Us About Missed Opportunities in Screening
Interval Breast Cancer (IBC) remains one of the most important quality markers in breast cancer screening programs. These are cancers diagnosed after a negative screening mammogram but before the next scheduled screen —and they represent the uncomfortable gray zone between biology, technology, and human interpretation. A recent large-scale study from Taiwan, analyzing 6.5 million screening mammograms in 2.88 million women , provides one of the most comprehensive insights into why interval cancers happen and how we can reduce them . 1. Dense Breasts: Still the Biggest Blind Spot The study confirms the firm association between breast density and the risk of IBC: Extremely dense breasts (BI-RADS D): IBC risk = 1.15 per 1000 person-years Fatty breasts (BI-RADS A): IBC risk = 0.29 per 1000 person-years That’s nearly a 4X increase . Dense breast tissue not only hides cancers but is also biologically more prone to aggressive tumors. For clinicians, th...