Global patterns and trends in the breast cancer incidence and mortality according to sociodemographic indices: an observational study based on the global burden of diseases

Objectives: Disparities in the global burden of breast cancer have been identified. We aimed to investigate recent patterns and trends in the breast cancer incidence and associated mortality. We also assessed breast cancer-related health inequalities according to socioeconomic development factors.

Design: An observational study based on the Global Burden of Diseases.

Methods: Estimates of breast cancer incidence and mortality during 1990-2016 were obtained from the Global Health Data Exchange database. Subsequently, data obtained in 2016 were described using the age-standardised and age-specific incidence, mortality and mortality-to-incidence (MI) ratios according to sociodemographic index (SDI) levels. Trends were assessed by measuring the annual percent change using the joinpoint regression. The Gini coefficients and concentration indices were used to identify between-country inequalities.

Results: Countries with higher SDI levels had worse disease incidence burdens in 2016, whereas inequalities in the breast cancer incidence had decreased since 1990. Opposite trends were observed in the mortality rates of high and low SDI countries. Moreover, the decreasing concentration indices, some of which became negative, among women aged 15-49 and 50-69 years suggested an increase in the mortality burdens in undeveloped regions. Conversely, inequality related to the MI ratio increased. In 2016, the MI ratios exhibited distinct gradients from high to low SDI regions across all age groups.

Conclusions: The patterns and trends in breast cancer incidence and mortality closely correlated with the SDI levels. Our findings highlighted the primary prevention of breast cancer in high SDI countries with a high disease incidence and the development of cost-effective diagnostic and treatment interventions for low SDI countries with poor MI ratios as the two pressing needs in the next decades.