Global cancer mortality among children, adolescents, and young adults from 77 countries, 1990-2021: a global time-series analysis and modelling study.

Background: The patterns of cancer burden in children, adolescents and young adults are distinct from those in the general adult population, underscoring the importance of developing targeted research and interventions. Thus, we analyzed global, regional, and national cancer mortality trends via the World Health Organization (WHO) Mortality Database among children aged 0-14 years and adolescents and young adults aged 15-34 across 77 WHO Member States.

Methods: Age-standardized country-specific cancer mortality rates (deaths per 100,000) and years of life lost between 1990 and 2021 were estimated via a locally weighted scatterplot smooth curve. We analyzed the associations between socioeconomic indices and mortality rates for 21 types of cancer. Furthermore, we conducted a decomposition analysis to understand the factors influencing mortality rates for these 21 types of cancer.

Results: Between 1990 and 2021, the age-standardized cancer mortality rate decreased from 12.35% [95% confidence interval (CI) 11.81%-12.88%] to 4.83% (95% CI 4.12%-5.54%) by - 3.29% per year. However, progress in reducing death rates has been heterogeneous in terms of country income, cancer site, and geography. In particular, the decrease in burden was most pronounced in North America; however, cervical and testicular cancer mortality is elevated in Africa, Latin America, and the Caribbean. While the major contributors to children's cancer mortality (leukemia, brain, and bone tumors) have remained unchanged for the past three decades, a significant decrease in respiratory tract cancer and an increase in colorectal cancer have led to a transition in the cancer profile in adolescents and young adults. Additionally, infection-related cancers are inversely correlated with socioeconomic indices; notably, colorectal cancer appears to have no correlation with these indices. We also revealed significant changes in mortality trends during the COVID-19 pandemic, which were more pronounced in children. Finally, a decomposition analysis revealed that the decrease in the number of cancer deaths worldwide between 1990 and 2021 may be attributed primarily to age-specific mortality rather than population growth or aging.

Conclusions: From 1990 to 2021, a significant decreasing trend in cancer mortality in the young population, especially in high-income countries, was observed. However, progress in reducing death rates has been heterogeneous by country income, cancer site, and geography, indicating disparities in control efforts across countries. Future studies are needed to address the exposures responsible for the heterogeneity of cancer burden and the changing cancer profile in this age group.