Global, regional, and national trends and inequality analysis of the total cancers and 29 cancer types from 1990 to 2021

Cancer poses a formidable challenge to global public health, with significant disparities in care access persisting across regions and socioeconomic groups. Utilizing data from the Global Burden of Disease 2021 study, we analyzed epidemiological trends for total cancers and 29 site-specific cancer types between 1990 and 2021. To quantify trends in cancer burden, we calculated the Estimated Annual Percentage Changes (EAPCs) in age-standardized incidence, mortality, and disability-adjusted life years (DALYs) from 1990 to 2021. We also examined the temporal trends in socio-demographic index (SDI)-related disparities across all cancer types by using the slope index of inequality (SII) and the concentration index (CI). Additionally, we calculated the Quality of Care Index (QCI) and explored its correlation with SDI using Pearson correlation coefficients. In 2021, the global incidence of total cancers reached 23.56 million cases, and we observed a growing trend in the age-standardized incidence. In contrast, the age-standardized mortality and disability-adjusted life years rates showed a downward trend. A substantial cancer burden was concentrated in high-SDI countries. Trends in global cancer inequality improved overall. We observed a significant shift in the burden of certain cancer types toward low-SDI regions in recent years, suggesting that the unequal distribution of the cancer burden has changed across regions. The correlation coefficient between the QCI and the SDI for total cancers was 0.87 in 2021. And the QCI was highly positively correlated with the SDI for 16 out of the 29 cancer groups, while non-melanoma skin cancer showed the lowest correlation. This study highlights that although global cancer treatment has improved and cancer deaths/DALYs inequality across countries has decreased, there are still challenges with high cancer incidence worldwide. Notably, cancer care quality remains closely correlated with the social development index. The distinctions between the 29 cancers have significant therapeutic ramifications, highlighting the significance of allocating resources and developing cancer treatment plans according to the kind of disease. Furthermore, these results provide insightful direction for the creation of future health policies.