Incidence rates vary nearly fourfold across the world regions, ranging from 27 per 100,000 in Middle Africa and Eastern Asia to 96 per 100,000 in Western Europe, and tend to be elevated in countries with highest development. Breast cancer is the most frequent cause of cancer death in women in less-developed regions (324,000 deaths, 14.3% of total) and the second cause of cancer death in more-developed regions (198,000 deaths, 15.4%), after lung cancer.
Incidence rates continue to increase in all countries except in a few high-income countries. In contrast, mortality rates are decreasing in many high-income countries but increasing in low- and middle-income countries. The variation in mortality rates between world regions (ranging from 6 per 100,000 in Eastern Asia to 20 per 100,000 in Western Africa) is less than that for incidence rates because of the considerably better survival from breast cancer in developed regions, resulting from increased access to early detection (mammography) and treatment. Differences in incidence between countries with and without mammography screening programs are also influenced by earlier diagnosis and the overdiagnosis associated with detecting breast cancers in asymptomatic women. Overall, a substantially greater proportion of women with breast cancer will die from their disease in less-developed regions.