Ma and Yu: Global Burden of Cancer 87 Figure 2. Type of Incident Cancer in Eastern Asia (male and female, age 15- 65+, 2002). Cases: 2,864,408. 488,596 (17.1%) Lung Figure 3. Types of Incident Cancer in North America (male and female, age 15- 65+, 2002). Cases: 1,561,046. 229,631 (14.7%) Breast 540,743 (18.9%) Stomach 225,635 (14.5%) Lung 409,697 (14.3%) Liver 272,846 (9.5%) Oesophagus 262,714 (9.2%) Colon and rectum 167,507 (5.8%) Breast 722,305 (25.2%) Other cancers 183,471 (11.85) Colon and rectum 70,004 (4.5%) Bladder 61,424 (3.9%) Non-Hodgkin lymphoma 257,942 (16.5%) Prostate 532,939 (34.1%) Other cancers 15.12 per 100,000 in North America; the rates in the same regions for those who were 65 years or older were 385.44, 1461.59, 2327.87 and 2958.14 per 100,000, respec- tively (Table 1). North America, Australia/New Zealand, and Europe had the highest overall incidence rates in 2002, while Northern and Western Africa had the lowest incidence rates (Tables 1-2). The ge- ographic variation was rather substantial. For example, the age-standardized rate in North American males (398.4 per 100,000 person-years) was four times of the age- standardized rate in North African males (99 per 100,000 person-years). The geographic disparity in cancer in- cidence is largely attributable to the various socioeconomic, environmental, and lifestyle factors in different regions of the world. Compared with developed countries, devel- oping countries in general may lack the re- sources to ascertain incident cancer cases. For example, in developed countries, many cases of breast, prostate, colon, and cervical cancers are identified through screening (e.g. mammography, prostate-specific anti- gen test, colonoscopy, and Pap smear), whereas in developing countries, large-scale screening efforts are usually uncommon. Genetic factors also play a role, but the dom- inant effect of genetics is only observed in a relatively small percentage of the popula- tion. It is believed that the majority of cancer cases (over 90 percent) are due to the joint effect of genetic variations, environmental factors, and lifestyle choices [2]. Geographic factor per se probably has little influence on cancer risk except sunlight exposure and vi- tamin D metabolism, both of which have been linked to cancer risk. The major cate- gories of cancer risk factors include tobacco use, occupational exposures, environmental contamination, infectious agents, and lifestyle factors. Tobacco use Knowledge about the role of tobacco smoking in the etiology of cancer has accu- mulated for many years [3]. In 2004, the IARC published a monograph on tobacco use and cancer, which concluded that tobacco contributed, to a greater or lesser extent, to cancer in 15 different sites, including lung, urinary tract, upper respiratory tract, pancreas, stomach, and liver. Although the prevalence of smoking has declined in many developed countries, it is in- creasing in developing countries [4]. Cur- rently, approximately 5 million people are killed annually by tobacco use; by 2030, esti- mates based on current trends indicate that this number will increase to 10 million, with 70 percent of deaths occurring in developing countries [5]. It is important to adopt policies such as tobacco tax increases, dissemination of information about health risks from smok- ing, restrictions on smoking in public places and in workplaces, comprehensive bans on