Age-related prognoses in a Luxembourgish breast cancer cohort

Breast cancer (BC) is the most common cancer among women worldwide, and age significantly influences prognosis. In July 2024, Luxembourg expanded BC screening programme (Programme Mammographie, PM), changing the eligible age from 50-69 to 45-74 years. This study assessed age-related BC prognosis before expansion.

This retrospective cohort study analysed 3,003 women diagnosed with invasive BC in Luxembourg (2013-2018) using National Cancer Registry data. Patients were stratified into four age groups: <40, 40-49, 50-69, and ≥70 years. Tumour characteristics, treatment, and five-year overall survival (OS) were compared across groups using Kaplan-Meier and Cox proportional hazards models.

Younger patients (<40 years) showed higher triple-negative tumours (24%, P<0.001) and chemotherapy use (78%). Five-year OS varied by age group, with the highest rates in women aged 40-49 (95.3%) and 50-69 (92.3%), followed by those <40 (91.0%), and lower survival in women ≥70 (65.4%) (P<0.001), a finding that partly reflects competing causes of mortality in this age group rather than BC prognosis alone. Screen-detected cases had better survival (95.8%). Advanced stage (hazard ratio [HR]=2.92, 95% confidence interval [CI]: 2.05-4.17) and triple-negative subtype (HR = 2.39, 95% CI: 1.69-3.38) linked to worse prognosis. Mastectomy (HR = 2.04) and absence of surgery (HR = 8.58) were associated with poorer survival, likely reflecting disease complexity rather than causal treatment effects.

Age at diagnosis influences BC prognosis through distinct tumour characteristics, including molecular subtype, histology, clinical stage, and mode of detection, which collectively impact treatment and survival. Women aged 40-49 and 50-69 achieved the most favourable survival outcomes. Among women in the established screening target group (50-69 years), early detection through organised mammography was associated with particularly high survival, reinforcing the value of standardised early detection in this group. Younger patients presented with more aggressive tumour biology, while older patients showed lower OS, an estimate that substantially reflects competing causes of death, including cardiovascular disease and other malignancies, in addition to any BC-attributable mortality disadvantage. These findings establish a baseline for evaluating expanded PM and highlight the need for age-specific strategies.