Ma and Yu: Global Burden of Cancer 93 America to a high of 0.69 in Africa [21]. The prognosis of certain types of malignancies, such as cervical cancer and colon cancer, can be remarkably improved by identifying cases early through effective screening. Less developed countries may lack resources to carry out large scale screenings. It is also possible that various completeness in cancer surveillance and vital records in more or less developed countries contributed to the ap- parent disparity. LOOKING INTO THE FUTURE Cancer is primarily a disease of old age. If all other factors remain the same, the de- mographic change (population growth and an increasingly higher percentage of older individuals in the world population) will lead to a global increase of cancer incidence. The GLOBOCAN 2002 database provides a means to project cancer incidence in the fu- ture. In 2002, there were an estimated total of 5,801,839 male individuals diagnosed with cancer (all sites except skin). If the age- specific incidence rates remain the same, population growth and aging of the world population would result in a projected total of 6,993,778 in 2010, a 20.5 percent increase within eight years (Table 4). The picture is similar for females. The total number of fe- males diagnosed with cancer (all sites except skin) is projected to change from 5,060,657 in 2002 to 6,037,753 in 2010, which repre- sents a 19.3 percent increase (detailed data not shown). This underscores the impor- tance to improve our understanding of the risk factors of cancer, design and implement practical prevention strategies, and develop better and more effective treatment options. The population compositions are dra- matically different between more and less developed countries. Less developed coun- tries have a smaller percentage of older indi- viduals (Figure 5). As cancer incidence increases with age, less developed countries have a larger population base and potentially more room for population aging. The fore- seeable increase in the global burden of can- cer likely will be more profound in less developed countries. In a recently published report, Cancer Control Opportunities in the Developing World [22], by the Institute of Medicine of the National Academy of Sci- ences, it is recognized that cancer is a sig- nificant disease burden in low- and middle-income countries, and the burden will become increasingly heavy for these countries not only because these nations are more populous, which give rise to more cases, but there are also more aggressive cancers and lower cure rates. The report also indicates that cancer causes and outcomes are very different between more and less de- veloped countries. For example, one in four cancer cases in developing countries are re- lated to infectious agents compared to less than one in 10 cases in the developed na- tions. These disparities suggest different cancer prevention and control strategies for more and less developed countries in direct- ing resources into the field of cancer re- search with regard to etiology, prevention, treatment, and health policy to reduce the burden of cancer globally. REFERENCES 1. Parkin DM, Bray F, Ferlay J, Pisani P. Global cancer statistics, 2002. CA Cancer J Clin. 2005;55(2):74-108. 2. Parkin DM. International variation. Onco- gene. 2004;23(38):6329-40. 3. Doll R, Peto R, Boreham J, Sutherland I. Mortality from cancer in relation to smoking: 50 years observations on British doctors. Br J Cancer. 2005;92(3):426-9. 4. World Health Organization. IARC. Tobacco smoke and involuntary smoking : Views and expert opinions of an IARC working group on the evaluation of carcinogenic risks to hu- mans, which met in Lyon; 2002 11-18 June. Lyon: IARC. 2004. 5. Jha P, Chaloupka FJ, Corrao M, Jacob B. Re- ducing the burden of smoking world-wide: effectiveness of interventions and their cover- age. Drug Alcohol Rev. 2006;25(6):597-609. 6. Siemiatycki J, Richardson L, Straif K, et al. Listing occupational carcinogens. Environ Health Perspect. 2004;112(15):1447-59. 7. Liang Y, Wong O, Yang L, Li T, Su Z. The development and regulation of occupational exposure limits in China. Regul Toxicol Phar- macol. 2006;46(2):107-13. 8. Lan Q, Zhang L, Li G, et al. Hematotoxicity in workers exposed to low levels of benzene. Science. 2004;306(5702):1774-6.