epidemiology 242: cancer epidemiology zuo-feng zhang, md, phd fall quarter, 2009

Epidemiology 242: Cancer Epidemiology

Zuo-Feng Zhang, MD, PhDFall Quarter, 2009

Overall Objectives of the Course

• The overall objectives are to introduce basic concept in cancer epidemiology, including concepts of carcinogenesis, multistage models, pre-malignant lesion, international patterns of cancer.

Overall Objectives of the Course

• To discuss major etiologic issues for a variety of cancers including smoking, alcohol drinking, virus, radiation, nutrition, occupational and environmental exposures.

• To review epidemiological data on major cancers including prostate, breast, lung, and other cancers.

• To lecture on the basic concepts of molecular and genetic epidemiology.

Introduction to Cancer Epidemiology

• (1) To overview the cancer magnitude

• (2) To familiarize students with basic concepts of tumor and its classification

• (3) To introduce basic concept of carcinogenesis and cancer epidemiology

Why Cancer is a Major Public Health Problem?

• Improved medical care and public health have lead to:

• Decrease and control of common diseases of childhood and infectious disease, the major causes of death in the past

• the increase of life expectation • the increase of the proportion of aging population,

since cancer is generally considered as an aging disease, cancer becomes a major public health problem.

Number of deaths for leading causes of death

• Heart disease: 631,636• Cancer: 559,888• Stroke (cerebrovascular diseases): 137,119• Chronic lower respiratory diseases: 124,583• Accidents (unintentional injuries): 121,599• Diabetes: 72,449• Alzheimer's disease: 72,432• Influenza and Pneumonia: 56,326• Nephritis, nephrotic syndrome, and nephrosis: 45,344• Septicemia: 34,234

Source: Table 1: Parkin DM, et al. CA Cancer J Clin [2005]; 55: 74-108

Incidence by sex and cancer site, World 2002

Mortality by sex and cancer site, World

Source: Table 1: Parkin DM, et al. CA Cancer J Clin [2005]; 55: 74-108

The Major CancersThe Major Cancers

• Lung (ICD-10 C33 and C34)Lung (ICD-10 C33 and C34)• Breast (female, C50)Breast (female, C50)• Colon/rectum (C18-C20)Colon/rectum (C18-C20)• Stomach (C16)Stomach (C16)• Prostate (C61)Prostate (C61)• Liver (C22)Liver (C22)• Cervix uteri (C53)Cervix uteri (C53)• Esophagus (C15)Esophagus (C15)

What is Cancer Epidemiology?

Definition • Cancer epidemiology is the study of the pattern of

cancer in populations.• Its essential aim is to identify causes of cancer,

including preventable (avoidable) causes and inherited tumor susceptibility.

• It is also play an critical role in many other areas of cancer research including evaluation of screening effects, cancer prevention and control

• Current studies directions includes molecular and genetic epidemiology of cancer.

Types of Epidemiologic Studies

• Descriptive Epidemiologic study: To describe the difference in occurrence of a particular cancer between different groups (age, gender, race, country, a period of time for time trend) and to generate the hypothesis for increased/decreased for the specific tumor type.

Types of Epidemiological Studies

• Analytic Epidemiology: To study risk factors or potential causes of cancer by a particular study design, e.g., case-control study or cohort study.

Types of Epidemiological Studies

• Intervention studies: Applying the knowledge (risk/protective factors) obtained from analytic epidemiological studies to specific population in order to reduce the risk of cancer.

Risk factors for Cancer

Percentage of Cancer Deaths Attributed to Various Factors (Doll R and Peto R, JNCI, 1981)

• Tobacco Use: 30% (25%-40%)• Diet:35% (10%-70%)• Infection: 10%? (1%-?)• Reproductive & Sexual Behavior: 7% (1%-13%)• Occupation: 4% (<2%-8%)• Alcohol: 3% (2%-4%)• Geophysical factors (natural radiation): 3% (2-4%)• Pollution: 2% (<1% – 5%)• Food additive: <1% (-5% – 2%)• Medicines and Medical Procedures: 1% (0.5%-3%)• Industrial consumer products <1% (<1%-2%)• Unknown: ?, ?

Harvard Center for Cancer Prevention (www.hsph.harvard.edu/cancer)

• Tobacco: 30%• Diet in adult life, including obesity: 30%• Sedentary lifestyle: 5%• Infectious agents: 5%• Defects in single genes that run in family: 5-

10%

Lichtenstein P, Holm NV, Verkasalo PK, Iliadou A, Kaprio J, Koskenvuo M, Pukkala E, Skytthe A, Hemminki K. NEJM, 2000

Chemical/environmental carcinogens

• Smoking and lung cancer• Sun exposure and squamous cell carcinoma of skin• Asbestos exposure and lung cancer• Smoke food risk with nitrosamines and

adenocarcinoma of the stomach• Alcohol drinking and squamous cell carcinoma of

esophagus• Aflatoxin B1 and liver cancer

Radiation

• Exposure to ultraviolet radiation (in the form of sunlight) and squamous cell carcinoma of skin

• Ionizing radiation is related to skin cancer and leukemia in radiologist

Viral factors

• HPV (human papilloma virus) and Cervix cancer• EBV(Epstein-Barr virus) and Nasopharyngeal cancer,

Burkitt’s lymphoma• HBV (hepatitis B virus) and hepatocellular carcinoma• HIV (human immunodeficiency virus) and Kaposi’s

sarcoma

http://www.yourdiseaserisk.wustl.edu/hccpquiz.pl?lang=english&func=home&page=cancer_index