The association between intrinsic breast cancer subtypes, mammography screening and prognosis: a large population-based real world cohort study

Introduction: Breast cancer (BC) as a heterogeneous disease is routinely managed according to its intrinsic subtypes. Mammographic BC screening reduces overall mortality in females. Our aim was to analyze the association between different intrinsic subtypes and mammography screening coverage (pre-screening-aged, screening-aged vs. post-screening-aged), attendance (attendance vs. non-attendance), and means of detection (screen-detected vs. interval BC) and BC survival. Materials and methods: We used a subpopulation of a registry including all patients diagnosed with invasive BC in Finland between 1995 and 2013. We collected screening results, information on biological characteristics and survival from national registries. Results: We included 7389 patients with early-stage BC. Compared to luminal A-like subtype, patients with triple-negative BC had the highest risks of death (HR: 1.81, 95 % CI: 1.52–2.15) and BC-related death (HR: 3.16, 95 % CI: 2.43–4.10). The majority of triple-negative BCs were diagnosed after the screening age. HER2-positive (non-luminal) tumors were most likely interval tumors, while the rest of the subtypes were most likely screen-detected. The risk of death was higher in patients with interval cancers compared to screen-detected cases (HR 1.40, 95 % CI: 1.18–1.68) and even higher among patients not attending screening (HR 2.17, 95 % CI: 1.75–2.68); this association was also detected in major subtypes. Conclusion: In this real-world dataset, triple-negative tumors had the highest risk of death and majority of these tumors were found after the screening age. In screening-aged females, patients with screen-detected tumors had the best survival, while patients with interval tumors and patients not attending screening had the worst prognosis.