Breast cancer patterns by age groups in Brazil: insights from population-based registries data.

Background: Breast cancer (BC) has exhibited varied epidemiological trends based on distinct age categories. This research aimed to explore the incidence and mortality rates of BC within pre-defined age groups in the Brazilian population.

Methods: BC incidence trends were assessed from 2010 to 2015 using Brazilian Population-Based Cancer Registries, employing age-standardized ratios and annual average percentage change (AAPC). Hospital-Based Cancer Registries provided clinical and sociodemographic data from 2000 to 2019. Mortality data were obtained from the National Mortality Information System from 2000 to 2020. Three groups were compared: < 40, 40-69, and ≥ 70 years.

Results: From 2010 to 2015, 205,966 new BC cases were recorded, with incidence rates of 7.1/100,000 for < 40, 156.5/100,000 for 40-69, and 247.5/100,000 for ≥ 70 years. The < 40 years group exhibited a significant increase in incidence rate (AAPC + 1.6; 95% CI: 1.0 to 2.2; p < 0.001). This age group also showed a higher proportion of black patients (53%, p < 0.001), alcohol consumption (20.5%, p < 0.001), proportion of patients treated at stages ≥ IIB (64.0%, p < 0.001), and a higher likelihood of receiving multiple treatment modalities (60.7%, p < 0.001). The ≥ 70 years group experienced a longer delay exceeding 60 days from diagnosis to treatment onset (54%, p < 0.001), while exhibiting a higher proportion of endocrine therapy utilization (45.3%, p < 0.01). Mortality rates increased across all subgroups, with the < 40 years group showing the most pronounced increase (AAPC + 1.8%; 95% CI: 1.6 to 2.1; p < 0.001).

Conclusion: These results highlight marked disparities in BC incidence, mortality rates, clinicopathological and sociodemographic characteristics between women under 40, and those in the 40-69 and ≥ 70 age groups in Brazil.