Cancer Epidemiology

Introduction to Cancer Epidemiology

What this course is about • Learning more about cancer epidemiology • Investigating risk factors implicated in cancer development • Learning to write grants and critique articles • Learning to be passionate about chronic disease epidemiology

True or False? Smoking causes lung cancer

True or False? Large percentage of cancers are preventable

True or False? In the past 20 years tremendous improvements in the treatment of all cancers have been achieved

True or False? Preventing cancer is easier than treating cancer

True or False? Screening tests are available for most cancers

Epidemiology “Distribution and

determinants of disease frequency in human populations”

Cancer Epidemiology Historical Perspective 1775 British surgeon, Percival Pott reported probably the first description of occupational carcinogenesis in the form of scrotum cancer （ men’s

Reproductive system ） among chimney sweeps.

Cancer Epidemiology Historical Perspective Tight corsets and cancer

1842 Rigoni-Stern, Italian physician, observed that married women in the city were getting cervical cancer, but nuns in nearby convents weren’t. He also observed that nuns had higher rates of breast cancer, and suggested that the nuns’ corsets were too tight.

Five Criteria for a Cause  Effect Relationship Criteria

Risk Factor for Disease

1) Timing

♦ Exposure occurs before

2) Strength

♦ Is dose-dependent ♦ Cessation of exposure can modify disease ♦ Occurs in multiple populations ♦ Is independent ♦ Can also act synergistically ♦ Produces structural‡ or functional changes

3) Prevalence 4) Relationship to other risk factors 5) Plausibility

development of disease or during its progression

which are events in mechanism of disease ‡

anatomic or molecular

Cancer Epidemiology Historical Perspective 1700s: tobacco and cancer Reports of cancer risks associated with tobacco in the 18th century included snuff taking and nasal cancer, reported by Hill in 1761, and pipe smoking and lip cancer by von Soemmering in 1795.

Cancer Epidemiology Historical Perspective • • • • • • • •

Tobacco and Lung Cancer Asbestos and Lung Cancer Leather Industry and Nasal Cancer Dyes and Bladder Cancer Ionizing Radiation and Many Cancers DES and Vaginal Adenocarcinoma EBV and Burkitt’s Lymphoma HPV and Cervical Cancer

Cancer Epidemiology An Introduction • • • • • •

The Epidemiologic Perspective Aims of Cancer Epidemiology Methods of Epidemiology Historical Perspective and Examples Contemporary Studies The Future

Aims of Cancer Epidemiology • Uncover new etiologic leads – study of the distribution of cancer – quantify the risk associated with different exposures and host factors

• Promote insights into the mechanisms of carcinogenesis • Assess efficacy of preventive measures • Investigate predictors of survival

Types of Epidemiologic Studies • • • •

Cohort Case-Control Cross-Sectional (Prevalence) Other

Methods of Cancer Epidemiology • Descriptive Studies – – – –

Incidence, mortality, survival Time Trends Geographic Patterns Patterns by Age, Gender, Ethnicity

• Analytic Studies – Case-control – Cohort

Challenges to Interpretation – Observational vs. Experimental Design – Cancer “clusters” – Study Design and Conduct • Study Size • Biases: Misclassification, confounding, selection

– – – –

Exposure assessment important Epidemiology and “strong” and “weak” effects Impact on a population level Replication critical

Cancer Epidemiology Sources • US SEER Registry System • IARC International Registries • State/Hospital Registries • Etiologic Clues – “Alert” Clinician – Experimental Studies

Cancer Epidemiology Current/Future Topics • • • • • • • • •

Infectious Agents Cancer and inflammation Obesity Physical Activity Diet Hormones Immunologic Factors Cancer disparities Inherited Susceptibility (Polymorphisms)

Cancer Epidemiology Current/Future Topics • • • • • • •

Tumor (somatic) Alterations Cancer Classification Biomarkers of Exposure/Effect Vaccines Survivorship Cancer and disability Alternative therapy