Introduction to Cancer Epidemiology

Faina Linkov, PhD

Research Assistant Professor of Medicine and Epidemiology

University of Pittsburgh Cancer Institute

E-mail (preferred mode of communications): fyL1 (at) pitt.edu

University of Pittsburgh Graduate School of Public Health, one of the oldest school to advocate for chronic disease epidemiology

research

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 EpidemiologyHistorical Perspective

1775British surgeon, Percival

Pott reported probably the first description of

occupational carcinogenesis in the

form of scrotum cancer among chimney sweeps.

Cancer EpidemiologyHistorical 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 development

of disease or during its progression

2) Strength Is dose-dependent Cessation of exposure can modify disease

3) Prevalence Occurs in multiple populations

4) Relationship to

other risk factors

Is independent Can also act synergistically

5) Plausibility Produces structural‡ or functional changes

which are events in mechanism of disease

‡ anatomic or molecular

Cancer EpidemiologyHistorical 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 EpidemiologyHistorical 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 EpidemiologyAn 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, SES, 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 EpidemiologySources

• US SEER Registry System

• IARC International Registries

• State/Hospital Registries

• Etiologic Clues– “Alert” Clinician– Experimental Studies

Cancer EpidemiologyCurrent/Future Topics

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

Cancer EpidemiologyCurrent/Future Topics

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