Lifestyle-induced cancer in South Africa

Abstract

Worldwide, there were approximately 10.1 million new cases, 6.2 million deaths and 22.4 million persons living with cancer in the year 2000. This represents an increase of 19% in incidence and 18% in mortality since 1990, in keeping with population growth and ageing. In terms of incidence, the most common cancer worldwide (excluding non-melanoma skin cancers) are lung, (12.3% of all cancers), breast (10.4%) and colorectal (9.4%). For any disease, the relationship of the incidence to mortality is an indication of prognosis. As lung cancer is associated with poor prognosis, it is also the largest single cause of death from cancer in the world (17.8% of all cancer deaths). Cancer of the stomach (10.4%) and liver (8.8%) rank second and third, respectively, in terms of deaths. Differences in the distribution between the sexes ar largely attributed to differences in exposure to risk factors rather than to variations in susceptibility. Generally, the relationship of incidence to mortality is not affected by sex.Although the risk of developing cancer is still higher in the developed regions of the world, the control of communicable diseases, as well as population ageing in developing countries, point to an increasing burden of cancer worldwide. Pisani et al. have projected a 30% increase in the number of cancer deaths in developed countries, and more than double this increase (71%) in developing countries from 1990 to 2010 because of demographic changes alone. The unequal distribution of cancer burden between the developing and developed world can largely be explained by differences in the distribution of aetiological risk factors, including infeectious agents and differences in lifestyle. Dietary factors are believed to be of major significance. Cancer is not a rare disease in Africa. In addition to the huge load of AIDS-related Kaposi's sarcoma, the probability of developing cancer by age 65 years in a female living in Kampala or Harare is only 20% lower than that of females in Western Europe. However, cancer treatment facilities in most of Africa are minimal.This chapter outlines the epidemiological and aetiology of the ten leading cancers in South Africa, with special emphasis, wherever possible, on South African research attempting to quantify the local burden of cancer and estimate the burden attributed to selected risk factors. Such studies are important in helping to better allocate resources towards the prevention and treatment of cancer. The focus will also be on research into the causes and prevention of these cancers. According to Doll and Peto about 75% of cancers in the United States in 1970 could have been avoided, and more recently, Parkin et al, estimated that there would have been 22.5% fewer cases of cancer in the developing world in 1990 if specific infections had been prevented. Lifestyle-induced cancer are likely to affect various population groups differently. Because of the diversity of cultures and lifestyles in the South African population, cancer burden, wherever possible, is preorted by age, sex, and population group.