Cancer Prevention

1. Dr Brenda Wilson Department of Epidemiology & Community Medicine Cancer Prevention

2. Global burden of cancer • IARC estimates of new cancer patients in 2000: • All countries ≈ 5,300,000 • Developed ≈2,500,000 • Less developed ≈2,800,000

3. Cancer is a disease of rich countries

4. But cancer is not necessarily a disease of rich people

5. Burden of cancer: Canada • 134,000 new cases per year • 65,000 deaths per year • Lifetime risk of developing cancer • males 40% • females 35%

6. Time trends – all cancers in Canada Standardized incidence rate per 100,000 500 400 300 200 100 0 1975 1980 1985 1990 1995 2000 Year Females Males

7. Geographical variation in Canada Fewestcases Most

8. Canada: commonest male cancers Standardized rate per 100,000 (1998)

9. Time trends: male cancers Standardized incidence rate per 100,000

10. Canada: commonest female cancers Standardized rate per 100,000 (1998)

11. Time trends: female cancers Standardized rate per 100,000

12. 100 80 60 40 20 0 1975 1980 1985 1990 1995 2000 Year Males Females Time trends: lung cancer Standardized incidence rate per 100,000

13. Lung cancer - men Fewest Most

14. Lung cancer - women Fewest Most

15. Lung cancer risk factors • Tobacco • Occupational exposures – asbestos, arsenic, polycyclic aromatic hydrocarbons, chromium, silica, nickel • Radon, radon daughters (occupational, domestic) • Protective effect of fruit & vegetables? • Genetic predisposition

16. 70 60 50 40 30 20 10 0 1975 1980 1985 1990 1995 2000 Year Males Females Time trends: colorectal cancer Standardized incidence rate per 100,000

17. Colorectal cancer – men & women

18. Colorectal cancer risk factors • Family history • Diet • Ulcerative colitis & Crohn’s disease • Obesity • Lack of exercise (colon)

19. 15 10 5 0 1975 1980 1985 1990 1995 2000 Year Males Females Time trends: melanoma Standardized rate per 100,000

20. Melanoma – men & women

21. Melanoma risk factors • Gender • Fair skin • UV exposure patterns • Tanning predisposition • Number of naevi • Dysplastic naevi • Family history

22. Time trends: breast cancer Standardized rate per 100,000

23. Breast

24. Breast risk factors • Age • Family history • Obesity • Hormonal effects • nulliparity • age of first pregnancy • early menarche • late menopause • Socioeconomic status • Benign breast disease (some) • Radiation to chest

25. Time trends: cervix cancer Standardized rate per 100,000

26. Cervix

27. Cervical cancer risk factors • Age at first intercourse • Number of sexual partners • Age • Smoking habit • Socioeconomic status • Oral contraceptive use • Nutritional deficiencies?

28. 140 120 100 80 60 40 20 0 1975 1980 1985 1990 1995 2000 Year Time trends: prostate cancer Standardized rate per 100,000

29. Prostate

30. Prostate risk factors • Fat consumption • Androgens • Ethnic group • Family history • ?role of vitamins

31. Estimated preventable cancer deaths • Smoking 30% • Diet 20-50% • Infections 10-20% • Reproductive hormones 10-20% • Alcohol 5% • EM radiation 6% • Occupational exposures 3% • Pollution up to 5%

32. Risk factors • Tobacco • Diet & exercise • UV exposure • Viral infection • Genetic susceptibility

33. Tobacco in Canada • 29% of adults smoke (>6m) • 1.4 million children exposed to tobacco smoke at home • Complete elimination of smoking could prevent >38,000 cancer cases, 18,000 cancer-associated deaths annually

34. Available interventions • Individual • smoking prevention • smoking cessation • healthier diet • Societal level • Restrict availability • Restrict advertising • increase cost • smoking bans

35. Diet & exercise in Canada • Most Canadians not meeting even minimum recommendations for fruit & vegetable consumption, most unaware of recommendations • 57% inactive during leisure time • Daily diets high in vegetables and fruit decrease cancer incidence by 20% • Healthy diet, physical activity, body mass reduces cancer incidence by 30-40% • Improve nutrition, reduce obesity – could prevent >161,000 cancer cases, 12,000 deaths

36. Available interventions • Individual • Healthy eating campaigns, initiatives • Food preparation tips • Shopping skills • Physical activity in school curricula • Societal • Food fortification • Increase access to healthier foods • Increase nutritional information • Increase accessibility of places for physical activity

37. UV radiation in Canada • Repeated exposure to the sun related to risk of melanoma – 66 000 new cases in 1999 in Canada • Half of adults do not adequately protect themselves against the sun. About 45% parents report that at least one of their children was sunburned at least once in the past summer • Reduction of over-exposure to sun – prevents ?13,800 melanoma cases

38. Available interventions • Individual • Education • Societal • School policies • Occupational protection • Availability of protection

39. Viral infections – available interventions • Cervical cancer • Education • Barrier methods of contraception • Vaccines?

40. Environmental carcinogens • Tobacco smoke, pesticides, radon, chlorinated disinfection by-products in drinking water • Overall exposure 3-9% • Few studies • Exposure to carcinogens – we don’t know