The Future of Primary Prevention and Early Detection of Cancer: A Scan of the Literature

Table 2: Increases in average annual number of cases of cancer and changes due to increase in Executive Summary 1. Cancer prevention must be future oriented because: • for 80 percent of those who will be suffering from cancer in 10 years time, cancer has already been initiated and has already been diagnosed in 10 percent of them; • put another way, the process of developing cancer is already under way in roughly one million people in Ontario today, if the latency period is assumed to be about 20 years; • conversely, in only 5 percent of those who will be suffering from cancer in 15 years time has the process already begun; • it takes time for the impact of prevention to be felt. Miller (1999) suggests-at least 30 years for tobacco control-10-60 years for dietary modification-40 years for Hepatitis B vaccination-at least 30 years for human papilloma virus vaccination. 2. The potential impact of cancer prevention is very large: • 22 percent of cancer cases in Canada could be prevented through the elimination of smoking (Miller, 1999) • 20 percent or more of all cases of cancer could be reduced by a shift to a high fruit and vegetable diet (WCRF/AICR, 1997) • 30-40 percent of all cases of cancer are preventable by a combination of dietary change, increased physical activity and maintenance of appropriate body weight (WCRF/AICR, 1997). However, since half of all cancer occurs in the 12 percent of the population aged 65 and over, the actual number of cases will increase significantly as the population ages and as cancers already initiated become apparent. 3. Further development of our understanding of the process of carcinogenesis suggests that cancer prevention in the future will feature a growing focus on prevention of the initiation and progression of carcinogenesis. This will require: • prevention of exposure to exogenous chemical, infectious and physical mutagens in the domestic, occupational, community and general environments; • strengthening resistance to cancer initiation, promotion and progression at the molecular and cellular levels. 4. Advances in our knowledge of carcinogenesis will result in the identification of a growing number of biomarkers of carcinogenesis, making it possible to: • identify cancer in the earliest stages of its development; • monitor the effectiveness of cancer prevention measures at an early stage. 6 5. Advances in genomics will make it possible to identify sub-populations who are more genetically susceptible …