Is the incidence of advanced‐stage breast cancer affected by whether women attend a steady‐state screening program?

In this cross‐sectional population‐based study, we assessed the incidence of advanced breast cancer based on screening attendance. Women from the Netherlands Cancer Registry were included if aged ≥49 years and diagnosed with breast cancer between 2006 and 2011, and data were linked with the screening program. Cancers were defined as screen‐related (diagnosed <24 months after screening) or nonscreened (all other breast cancers). Two cut‐offs were used to define advanced breast cancer: TNM‐stage (III–IV vs 0–I–II) and T‐stage alone (≥15 mm vs <15 mm or DCIS). The incidence rates were adjusted for age and logistic regression was used to compare groups. Of the 72,612 included women diagnosed with breast cancer, 44,246 (61%) had screen‐related breast cancer. By TNM stage, advanced cancer was almost three times as likely to be at an advanced TNM stage in the nonscreened group compared with the screen‐related group (38 and 94 per 100,000, respectively; OR: 2.86, 95%CI: 2.72–3.00). By T‐stage, the incidence of advanced cancer was higher overall, and in nonscreened women was significantly higher than in screened women (210 and 169 per 100,000; OR: 1.85, 95%CI: 1.78–1.93). Data on actual screening attendance showed that the incidence of advanced breast cancer was significantly higher in nonscreened women than in screened women, supporting the expectation that screening would cause a stage shift to early detection. Despite critical evaluations of breast cancer screening programs, our data show that breast cancer screening is a valuable tool that can reduce the disease burden in women.