Burden of Cancer in Developing Countries
Data from Ferlay and others (2004) clearly illustrate the differing patterns of cancer incidence in developing and developed countries (figures 29.1 and 29.2). In developing countries, the top five female cancers in rank order of incidence are breast, cervical, stomach, lung, and colorectal cancer; however, cervical cancer still accounts for more deaths than breast cancer in developing countries. The top five male cancers are lung, stomach, liver, esophageal, and colorectal cancer (figure 29.1). The incidence of cancers of the lung and breast is relatively high in both developed and developing countries. Colorectal cancer accounts for a smaller share of the burden in developing countries than in developed countries, but cancer of the stomach accounts for a higher share. Some cancers that are more common in developing than in developed countries, including stomach, liver, and cervical cancer, are related to the absence of a well-developed public health infrastructure for the control of cancer-causing infectious agents and contaminants, the lack of basic preventive health care and screening services for much of the population, and the poor-quality diets available to the most economically disadvantaged members of society in many developing countries. Cancer of the esophagus, also relatively common in developing countries, may reflect, in part, the consumption of traditional beverages at extremely high temperatures. Some cancers that are increasingly common in developing countries, including lung, breast, and colorectal cancer, may reflect the increasing Westernization of lifestyles, longer life expectancy, and globalization of markets for tobacco products.
[Figure
29.1]
[Figure
29.2]
For some cancers, including esophageal, liver, lung, and pancreatic cancer, survival rates vary little between developing and developed countries (Sankaranarayanan, Black, and Parkin 1998). Currently available methods of early detection and treatment have not been demonstrated to be effective for these cancers, so primary prevention remains the most practical intervention for control. For a second group of cancers, including large bowel, breast, ovarian, and cervical cancer, proven methods of early detection, diagnosis, and treatment are available that can, in principle, be delivered through district health care facilities. For these cancers, survival rates vary both between developing and developed countries as a whole and between specific countries within each of these groups. For a third group of cancers, including testicular cancer, leukemia, and lymphoma, the variability in survival between developing and developed countries is tremendous. Even though relatively effective treatments are available for these cancers, they are multimodal treatments that require a relatively high level of medical resources, a good health care infrastructure, and a level of sophisticated knowledge, which low-and middle-income developing countries may not have.
Table 29.1 shows estimated cancer deaths and the estimated disease burden in terms of disability-adjusted life years (DALYs) lost as a result of various types of cancers in developing and developed countries and by region in 2001. As the table shows, the seven types of cancer that are the focus of this chapter account for seven of the first eight cancer sites ranked by number of deaths in developing countries. Considerable heterogeneity in the pattern of cancer burden across the six regions is apparent, and additional heterogeneity is apparent within these regions. Deaths from liver cancer are relatively high in East Asia and the Pacific and in Sub-Saharan Africa, probably because of the high prevalence of chronic HBV infection and the lack of adequate resources for food storage and preservation in those regions (Parkin and others 2003). The number of deaths from colorectal and breast cancer, as a proportion of all cancer deaths, is relatively high in Europe and Central Asia and in Latin America and the Caribbean, probably because those regions have increasingly adopted more Western lifestyle patterns of reproductive behavior, diet, and physical activity. The number of deaths from oral cancer is particularly high in South Asia, where the use of betel quid is common.
[Table .]
