Global Statistics for Young Breast Cancer Under 35 Years: A Population-Based Study

Abstract

Background: Accurate and up-to-date estimates of the global burden of young breast cancer (YBC) under 35 years are scarce. This study aims to assess the global burden and trends of YBC, providing insights to inform global YBC control strategies.

Methods: We analyzed Global Burden of Disease (GBD) data from 1990 to 2021 to assess YBC incidence, prevalence, mortality, and disability-adjusted life-year (DALYs), including age-standardized rates (ASIR, ASPR, ASMR, ASDR). The study accounted for geographic variations and Socio-demographic index (SDI) quintiles, assessing trends and projecting rates to 2050 while examining risk factors. Primary outcomes were age-standardized rates and average annual percent change (AAPC).

Findings: In 2021, YBC accounted for substantial global disease burden, with 81,856 new cases (95% UI: 76,458-87,253), 687,819 prevalent cases (95% UI: 642,400-733,238), 18,597 deaths (95% UI: 17,191-20,003), and 1,178,721 DALYs (95% UI: 1,090,902-1,266,541). From 1990 to 2021, global ASIR (AAPC: 1.27%) and ASMR (AAPC: 0.32%) increased significantly, with projections indicating continued growth through 2050. While ASIR rose across all SDI quintiles, ASMR increased only in low and low-middle SDI quintiles (AAPC: 1.30% and 1.14%), but decreased in high and high-middle SDI quintiles (AAPC: -1.52% and -0.99%). 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.

Interpretation: 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.

Keywords: Young breast cancer, Global burden, Trends, Risk factor