Chapter 12: Cancer Epidemiology

The foundation emphasizes how altered DNA methylation patterns, impaired cellular repair mechanisms, chronic inflammation, hormonal dysregulation, and compromised stromal-immune interactions create conditions favorable for malignant transformation. Global cancer burden data reveals distinct geographic and socioeconomic patterns, with lung cancer representing the leading cause of cancer mortality worldwide, followed by breast, prostate, colorectal, stomach, and liver cancers. The chapter introduces developmental plasticity and the developmental origins hypothesis, demonstrating how maternal nutrition, in utero environmental exposures, and transgenerational epigenetic modifications predispose offspring to elevated cancer risk in adulthood, with historical examples including prenatal diethylstilbestrol exposure and famine-associated cancer vulnerability. Tobacco emerges as the leading preventable carcinogenic exposure, causally linked to multiple cancer types including lung, aerodigestive, bladder, renal, pancreatic, and cervical malignancies, while secondhand smoke exposure confers significant risk to nonsmoking populations. Nutritional epidemiology reveals protective effects of cruciferous vegetables, garlic compounds, and polyphenolic substances through nutrigenomic and epigenetic mechanisms, whereas processed and red meat consumption, elevated saturated fat intake, and refined carbohydrates increase colorectal and gastric cancer incidence. Obesity contributes to at least eleven distinct cancers through insulin-growth factor axis dysregulation, estrogen and androgen signaling alterations, adipokine-mediated inflammation, and metabolic dysfunction. Alcohol consumption, classified as a Group 1 carcinogen without a safe threshold, demonstrates dose-dependent associations with oropharyngeal, hepatic, colorectal, and breast malignancies. Physical activity provides protective effects against multiple cancer types by modulating insulin sensitivity, reducing systemic inflammation, enhancing natural killer cell mobilization, and promoting myokine-mediated tumor suppression. Environmental and occupational exposures including air pollutants, particulate matter, radon gas, ionizing radiation, ultraviolet radiation, and synthetic chemicals represent significant cancer risk factors across populations. Infectious agents including human papillomavirus types 16 and 18, hepatitis B and C viruses, Helicobacter pylori, Epstein-Barr virus, and parasitic organisms drive pathogen-associated malignancies through chronic inflammation and direct viral oncogenesis. The chapter emphasizes cancer prevention through exposure reduction, dietary modification, physical activity enhancement, infection prevention strategies, and occupational safety standards.