Inequalities in cancer incidence and mortality across medium to highly developed countries in the twenty-first century

Melina Arnold, Elisenda Rentería, David I. Conway, Freddie Bray, Tom Van Ourti, Isabelle Soerjomataram

Inequalities in the burden of cancer have been well documented, and a variety of measures exist to analyse disease disparities. While previous studies have focused on inequalities within countries, the aim of the present study was to quantify existing inequalities in cancer incidence and mortality between countries. Data on total and site-specific cancer incidence and mortality in 2003-2007 were obtained for 43 countries with medium-to-high levels of human development via Cancer Incidence in Five Continents Vol. X and the WHO Mortality Database. We calculated the concentration index as a summary measure of socioeconomic-related inequality between countries. Inequalities in cancer burden differed markedly by site; the concentration index for all sites combined was 0.03 for incidence and 0.02 for mortality, pointing towards a slightly higher burden in countries with higher levels of the human development index (HDI). For both incidence and mortality, this pattern was most pronounced for melanoma. In contrast, the burden of cervical cancer was disproportionally high in countries with lower HDI levels. Prostate, lung and breast cancer contributed most to inequalities in overall cancer incidence in countries with higher HDI levels, while for mortality these were mostly driven by lung cancer in higher HDI countries and stomach cancer in countries with lower HDI levels. Global inequalities in the burden of cancer remain evident at the beginning of the twenty-first century: with a disproportionate burden of lifestyle-related cancers in countries classified as high HDI, while infection-related cancers continue to predominate in transitioning countries with lower levels of HDI.