Cancer's Impact on Health
Cancer is a leading threat to health worldwide. In 2008, 12.4 million new cancer cases were diagnosed across the globe, with cancer accounting for 7.6 million deaths. Lung cancer is of particular significance; it is the most common cancer in the world, accounting for nearly 10% (1.2 million) of new cases, and is responsible for almost one in five (17%) of all cancer deaths, making it the most common cause. Cancer is much more common in older people, with 56% of all newly diagnosed cancer patients and 71% of cancer deaths occurring in people aged 65 years and older. Current demographic trends indicate population aging across the globe, particularly in developed countries. As the population ages, cancer incidence and mortality will increase dramatically, with global cancer deaths projected to increase by 45% between 2007 and 2030, and 12 million annual deaths estimated by 2030.
These projections are based on cancer rates remaining consistant with current figures. However, there is a large body of evidence to indicate that cancer rates are highly variable – differing considerably over time[3,4] and in individuals who migrate from one region to another[5,6] – and modifiable. A classic paper by Doll and Peto in 1981 was one of the first to identify how much of cancer could be explained by potentially modifiable risk factors. The authors compared site-specific cancer rates in the USA with the lowest incidence rates reported worldwide, with the assumption that the excess reflected the degree of cancer that could be potentially prevented. Doll and Peto concluded that only a small percentage of cancers were owing to inherited genetic factors, and that 75–80% of cancers in the USA could have been avoided through environmental factors, including use of tobacco and alcohol, physical activity, diet, biological factors (e.g., birthweight, age at puberty and reproduction) and occupational and environmental exposure. This article provided a first look at this issue and was a landmark in cancer prevention research. In the several decades following publication of this paper, additional risk factors (such as obesity) have been identified, as well as the development of more sophisticated statistical modeling approaches. These efforts have led to some variation in the estimates of the specific percentage of risk that can be attributed to modifiable risk factors, depending on the assumptions employed. However, many contemporary estimates converge around 50%; that is, half of cancers could be prevented through changing modifiable risk factors.[5,8,9] Preventability may be even higher for specific cancers in some subgroups, such as colorectal cancer in middle-aged men, where the risk attributed to modifiable risk factors has been estimated at 71%.
A considerable body of literature now supports two conclusions: cancer can be prevented and many of the most powerful preventive strategies are based on changing lifestyles and modifying risks. Major modifiable risk factors include tobacco use (the most significant), and (in alphabetical order) infection, nutrition, obesity and physical activity. Evidence relating to the role of these risk factors in cancer incidence will be briefly reviewed; see Table 1,[1,5]Table 2[11,12] and Table 3 for an overview. This effort is greatly facilitated owing to the availability of several comprehensive reviews of the vast literature available, in particular, two reports from the World Cancer Research Fund and the American Institute for Cancer Research (for reviews of nutrition, physical activity and obesity, referred to in this paper as the WCRF/AICR Report I; and of policy implications, referred to as the WCRF/AICR Report II), as well as a number of important reports from the WHO.
It should be noted that this review focuses on factors believed to account for the largest numbers of cancers; however, other modifiable risk factors, such as exposures to the sun, ionizing radiation, and occupational and environmental carcinogens, are also significant targets for cancer prevention, particularly for certain cancers. In addition to describing evidence linking various risk factors to cancer, we will discuss current recommendations and provide an example of contemporary activities related to reducing the risk. Reviewing the full extent of cancer prevention interventions is beyond the scope of this review, and the reader is referred to a comprehensive review prepared by the US Institute of Medicine and other sources cited in each section.
Expert Rev Pharmacoeconomics Outcomes Res. 2010;10(2):143-154. © 2010 Expert Reviews Ltd.
Cite this: Cancer Prevention: Major Initiatives and Looking into the Future - Medscape - Apr 01, 2010.