Interval Breast Cancer Versus Screen-Detected Cancer: Comparison of Clinicopathologic Characteristics in a Single-Center Analysis

Interval breast cancers (IBC) have been of great concern since breast mammogram screening programs were introduced. We compared IBC to screen-detected cancers (SDC). IBC accounted for one-fifth of all breast cancers diagnosed in women who followed the regional screening program. IBC appeared to be more aggressive than SDC in terms of tumor invasiveness, size, and St Gallen molecular subtype, leading to worse overall and disease-free survival. Background The introduction of breast screening programs has raised the problem of interval breast cancers (IBC). The aims of this study were to analyze the impact of IBC on the screening program, to compare IBC and screen-detected cancers (SDC), and to identify possible predictors of mortality. Patients and Methods Patients with breast cancer diagnosed during the regional breast screening program between January 2008 and December 2013 at a single center in Italy were included. Demographic, preoperative, and postoperative data were prospectively collected and retrospectively analyzed. Results Five hundred thirty-four patients were enrolled; 106 women (19.9%) had IBC and 428 women (80.1%) SDC. IBC presented more aggressive features compared to SDC, such as tumor invasiveness (95% vs. 85%; P =.005), tumor size (≥ pT2 37% vs. 21%; P =.001), grade (G3 39% vs. 17%; P <.001), and St Gallen molecular subtype (triple negative 22% vs. 7%; P <.001), resulting in higher distant recurrence rate (8% vs. 2%; P =.009) and worse overall and disease-free survival (P =.03 and P =.001, respectively). Cox multivariate regression analysis identified St Gallen molecular subtype as the only predictor of mortality in patients with breast cancer (P =.03). Conclusion IBC accounted for one-fifth of all breast cancers diagnosed in women who followed the regional screening program. Furthermore, IBC appeared to have more aggressive features compared to SDC, leading to worse survival. These worse survivals depended on St Gallen molecular subtype