Population-based analysis of breast cancer incidence and mortality: overall and age-specific temporal trends over 40-year period in Girona, Spain.

Purpose: Breast cancer (BC) incidence and mortality in women have changed over time. This study aims to analyze population-level incidence and mortality trends over 40 years of observation.

Methods: Population-based study of BC conducted by Girona Cancer Registry covering the period 1980-2019. Age-standardized incidence and mortality rates were calculated. Poisson change-point regression models were used to analyze trends, calculating the annual percentage change (APC).

Results: A total of 12,283 diagnoses of invasive BC between 1980 and 2019. The overall age-standardized incidence rate was 109.9 (95% confidence intervals (CI) 104.4; 115.4) cases per 100,000 women-years. Trend analyses showed a statistically significant incidence increase of 4.2% per year from 1980 to 1994 (95%CI 3.3; 5.1), and a stabilization between 1994 and 2019, with an APC of 0.28% (95%CI - 0.04; 0.56). These trends were similar for the age groups 0-49 years and 50-69 years. In women over 69 years of age, an increase in incidence of 4.4% (95%CI 2.8; 6.0) per year was observed between 1980 and 1995 followed by a non-statistically significant decrease of - 0.35% (95%CI - 0.86; 0.15) between 1995 and 2019. The overall age-standardized mortality rate was 30.3 (95%CI 29.3; 31.3) cases per 100,000 women-years. Mortality rate trends showed a statistically significant decrease of - 1.87% (95%CI - 2.38; - 1.37) per year since 1992.

Conclusion: There has been a stabilization in the incidence of BC and a gradual decline in BC mortality in women. The introduction of mammography in the mid-1990s, alongside early detection and treatment due to screening programs may play a significant role in the reduction of BC burden in women of all ages.