General Oncology

CANCER EPIDEMIOLOGY

Anita Kumar

Victoria Blinder

Cancer Epidemiology Research Methods

Epidemiology: Study of distribution, determinants, & outcomes of cancer at a population level; applies public health or policy perspective, rather than the perspective of an individual pt
“Efficacy”: Treatment demonstrates an effect, often in a clinical trial, vs. “effectiveness”: Effect in “real-world,” at the population level
Observational studies: Cross-sectional, cohort, & case-control
Experimental studies: Individual-based vs. community-based
Epidemiology research can include analyses of patterns of care, comparative outcomes, cost-effectiveness, & health care disparities.
A classic study showed women w/breast cancer who are uninsured or on Medicaid had a higher risk of death compared to women w/private insurance (NEJM 1993;329:326).
Molecular & genetic epidemiology: Identification of biomarkers & genetic features linked to cancer susceptibility

Cancer Cases and Deaths

U.S. cancer incidence trends 1998-2008 (ACS Cancer Facts & Figures 2012):

Cancer is a disease of older individuals, incidence ↑ w/aging population
↓ in lung cancer due to decline in smoking
↓ in colorectal, cervical cancer w/early detection, screening
↓ in stomach cancer due to ↓ in H. pylori infection
↓ in prostate cancer incidence due to ↓ in PSA screening
Stable breast cancer incidence (period of decline in 2002-2003 due to ↓ in HRT use)
↑ incidence of HPV-related oropharyngeal cancer, esophageal adenocarcinoma, liver & intrahepatic bile duct, pancreas, thyroid, melanoma of skin, & kidney cancer

Figure 1-1

Global Cancer Epidemiology

Temporal trends: (1) Cancer incidence is ↑ in the developing world due to

↑ longevity, & growing adoption of Western diet, physical inactivity, & tobacco use; (2) ↓ incidence of cancers due to infectious etiologies (stomach, liver, uterine cervix)
Environmental factors that contribute to geographic distribution of cancer, eg, stomach cancer incidence rates highest in Eastern Asia & Central/Eastern Europe due to chronic H. pylori infection & diets high in salt & processed foods, low in fresh fruits & vegetables
Migration studies: Japanese migrants to California have lower rates of gastric cancer compared to country of origin, but higher than California residents (Cancer 1965;18:656)

Etiologic Agents in Cancer

Agent	Cancer(s)
Tobacco:
33% of cancer deaths in the United States are caused by smoking (IARC: World Cancer Report: 2010) In 1950, the first large studies published linking smoking & lung cancer (BMJ 1950;2:739; JAMA 1950;143:329) Tobacco-related carcinogenesis: Tobacco → multiple carcinogens → covalent bonds formed w/DNA → DNA adducts → miscoding → mutations	Lung, larynx, nasal, oral cavity, esophagus, liver, pancreas, cervix, bladder, leukemia, & colorectal
Infectious:
Hepatitis C Virus	Liver
Hepatitis B Virus	Liver
Epstein Barr Virus	Burkitt lymphoma, nasopharynx, Hodgkin lymphoma
Herpes Simplex Virus 8	Kaposi sarcoma, pulm effusion lymphoma, Castleman disease
HPV	Anogenital & oral cavity
Polyomavirus	Merkel cell carcinoma
JC virus	Progressive multifocal leukoencephalopathy
HTLV-1	Adult T-cell leukemia/lymphoma
HIV-associated	Kaposi sarcoma, cervix, various NHL
H. Pylori	Stomach
Schistosomiasis	Bladder (squamous cell)
Inflammation:
Acute & chronic inflammation contributes to multiple cancers	Reflux esophagitis → Barrett esophagitis → esophageal cancer Liver cirrhosis: Liver cancer Chronic pancreatitis: Pancreas cancer
Chemical Factors:
Asbestos, silica	Lung, mesothelioma
Radon, nickel dust, arsenic, chronium	Lung
EtOH	Oral cavity, esophagus, liver
Aromatic amines	Bladder
Cadmium	Prostate
Benzene	Leukemia
Smoked, salted, pickled foods	Stomach
Aflatoxin	Liver
Estrogen (HRT)	Breast, endometrial
Androgen	Prostate
Immunosuppressants	NHL
Physical Factors:
IR (Chernobyl, atomic bomb)	Thyroid, leukemia, other solid tumors
UV light	Skin cancers
Lifestyle Factors:
Obesity	Breast, endometrial, prostate, esophagus
Diet—complex exposure
Beta-carotene (JAMA 2003;290:476, JNCI 1996;88:1550)	↑ lung cancer deaths

CANCER PREVENTION & SCREENING

Payal D. Shah

Victoria Blinder

General Principles

Primary cancer prevention: To reduce cancer incidence & mortality; eg, smoking cessation, sun avoidance, cancer virus vaccination, chemoprevention
Screening: Method of secondary cancer prevention; to identify asx cancers w/the goal of earlier interventions & mortality reduction
Note various guidelines (USPSTF, NCCN, ACS, ASCO, etc.) differ