Global patterns and risk factors of breast cancer in women under 35: a population-based study

Accurate estimates of the global burden of young breast cancer (YBC) are lacking. In 2021, YBC accounted for substantial global disease burden, with 81,856 new cases, 687,819 prevalent cases, 18,597 deaths, and 1,178,721 DALYs. From 1990 to 2021, global ASIR (AAPC: 1.3%) and ASMR (AAPC: 0.3%) increased significantly, with projections indicating continued growth through 2050. While high-SDI quintiles currently bear the greatest burden of YBC incidence and prevalence, low-SDI quintiles are experiencing faster growth rates. While ASIR rose across all Socio-demographic index (SDI) quintiles, ASMR increased only in low and low-middle SDI quintiles (AAPC: 1.3% and 1.1%) but decreased in high and high-middle SDI quintiles (AAPC: 1.5% and -1.0%). Except for the lowest SDI quintile, YBC proportion within overall breast cancer burden decreased across other SDI quintiles. Dietary risks were the primary driver of YBC mortality, while high BMI showed an inverse association with mortality. YBC represents a growing global burden with significant disparities across SDI quintiles. Targeted interventions to address modifiable risk factors and improve healthcare access in less developed regions are essential to mitigate its impact.