Cancer Prevention Dr Brenda Wilson Department of Epidemiology & Community Medicine

Department of Epidemiology & Community Medicine 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

Department of Epidemiology & Community Medicine Cancer is a disease of rich countries

Department of Epidemiology & Community Medicine But cancer is not necessarily a disease of rich people

Department of Epidemiology & Community Medicine Burden of cancer: Canada 134,000 new cases per year 65,000 deaths per year Lifetime risk of developing cancer –males 40% –females 35%

Department of Epidemiology & Community Medicine Time trends – all cancers in Canada Year FemalesMales Standardized incidence rate per 100,000

Department of Epidemiology & Community Medicine Geographical variation in Canada Fewest cases Most

Department of Epidemiology & Community Medicine Canada: commonest male cancers Standardized rate per 100,000 (1998)

Department of Epidemiology & Community Medicine Time trends: male cancers Standardized incidence rate per 100,000

Department of Epidemiology & Community Medicine Canada: commonest female cancers Standardized rate per 100,000 (1998)

Department of Epidemiology & Community Medicine Time trends: female cancers Standardized rate per 100,000

Department of Epidemiology & Community Medicine Time trends: lung cancer Year MalesFemales Standardized incidence rate per 100,000

Department of Epidemiology & Community Medicine Lung cancer - men Fewest Most

Department of Epidemiology & Community Medicine Lung cancer - women Fewest Most

Department of Epidemiology & Community Medicine 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

Department of Epidemiology & Community Medicine Time trends: colorectal cancer Year MalesFemales Standardized incidence rate per 100,000

Department of Epidemiology & Community Medicine Colorectal cancer – men & women

Department of Epidemiology & Community Medicine Colorectal cancer risk factors Family history Diet Ulcerative colitis & Crohn’s disease Obesity Lack of exercise (colon)

Department of Epidemiology & Community Medicine Time trends: melanoma Year MalesFemales Standardized rate per 100,000

Department of Epidemiology & Community Medicine Melanoma – men & women

Department of Epidemiology & Community Medicine Melanoma risk factors Gender Fair skin UV exposure patterns Tanning predisposition Number of naevi Dysplastic naevi Family history

Department of Epidemiology & Community Medicine Time trends: breast cancer Standardized rate per 100,000

Department of Epidemiology & Community Medicine Breast

Department of Epidemiology & Community Medicine 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

Department of Epidemiology & Community Medicine Time trends: cervix cancer Standardized rate per 100,000

Department of Epidemiology & Community Medicine Cervix

Department of Epidemiology & Community Medicine Cervical cancer risk factors Age at first intercourse Number of sexual partners Age Smoking habit Socioeconomic status Oral contraceptive use Nutritional deficiencies?

Department of Epidemiology & Community Medicine Time trends: prostate cancer Standardized rate per 100,000 Year

Department of Epidemiology & Community Medicine Prostate

Department of Epidemiology & Community Medicine Prostate risk factors Fat consumption Androgens Ethnic group Family history ?role of vitamins

Department of Epidemiology & Community Medicine Estimated preventable cancer deaths Smoking30% Diet20-50% Infections 10-20% Reproductive hormones10-20% Alcohol 5% EM radiation6% Occupational exposures3% Pollutionup to 5%

Department of Epidemiology & Community Medicine Risk factors Tobacco Diet & exercise UV exposure Viral infection Genetic susceptibility

Department of Epidemiology & Community Medicine 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

Department of Epidemiology & Community Medicine Available interventions Individual –smoking prevention –smoking cessation –healthier diet Societal level –Restrict availability –Restrict advertising –increase cost –smoking bans

Department of Epidemiology & Community Medicine 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

Department of Epidemiology & Community Medicine 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

Department of Epidemiology & Community Medicine UV radiation in Canada Repeated exposure to the sun related to risk of melanoma – 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

Department of Epidemiology & Community Medicine Available interventions Individual –Education Societal –School policies –Occupational protection –Availability of protection

Department of Epidemiology & Community Medicine Viral infections – available interventions Cervical cancer –Education –Barrier methods of contraception –Vaccines?

Department of Epidemiology & Community Medicine 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