Epidemiology of Cancer

Study Notes

Cancer is a generic term for a group of over 100 diseases characterized by uncontrolled cell division and invasion of other tissues.
Cancer results from genetic changes (mutation) in a cell, causing tumor cells to behave differently from normal cells.
In 2020, there were 19.3 million new cancer cases and 10 million cancer deaths globally.
By 2030, it is projected that there will be approximately 26 million new cancer cases and 17 million cancer deaths per year.
56% of new cancer cases occur in developing countries, and 64% of cancer deaths occur in developing countries.
Breast cancer was the most commonly diagnosed cancer, followed by lung, colorectal, prostate, and stomach cancer.

Age distribution: The incidence rate of cancer increases steadily with age, with a median age of diagnosis of 66 years.
It kills more children (3-14 times) than any other disease.
Sex distribution:
- Higher incidence in men than in women, largely due to past exposure to tobacco smoking, alcohol consumption, and hazardous occupations.
- Thyroid and gallbladder cancers are more common in women, related to diet, overweight, and estrogen.
Geographical distribution:
- Higher in industrialized sectors and nations.
- Etiologic factors present in the biological, chemical, physical, or social environment contribute to the development of cancer.
Socioeconomic status (SES):
- People with lower SES have disproportionately higher cancer death rates than those with higher SES, regardless of demographic factors.

Biological agents:
- Parasites (e.g., schistosoma haematobium, liver flukes) associated with bladder cancer and cholangio-cellular carcinoma.
- Viruses (e.g., Hepatitis B, Epstein-Barr virus, Herpes virus) associated with liver cancer, Burkett's lymphoma, and cervical cancer.
Chemical agents:
- Asbestos, benzene, benzidin, mustard gas, and pesticides.
Pharmaceuticals:
- Post-menopausal hormonal therapy.
Obesity:
- Increases the risk of endometrial cancer, and probably increases the risk of breast, colon, and gallbladder cancer.
Physical activity:
- Reduces the risk of bladder, breast, endometrial, esophageal, kidney, and stomach cancer.
Diet:
- High correlation between dietary fat and colorectal, breast, endometrial, prostate, lung, and pancreatic cancers.
- Salt-preserved diet and contaminated food increase the risk of stomach and nasopharyngeal cancer.
- Diet rich in vegetables and fruits decreases the risk of many cancers.

1/3 of cancers are preventable, 1/3 are curable if detected early, and 1/3 are palliative to improve quality of life.
Aim of cancer control: Reduce cancer incidence, morbidity, and mortality through prevention, early diagnosis, treatment, and palliative care.
Prevention:
- Primary prevention:
  - Healthy diet
  - No smoking
  - No alcohol
  - Exercise/maintain optimal weight
  - Avoid radiation
- Prophylactic surgery (e.g., breast, colorectal, cervical cancer)
- Chemoprevention (e.g., tamoxifen for breast cancer, finasteride for prostate cancer)

Secondary prevention:
- Early detection of cases after symptoms have developed (through community education)
- Early detection in asymptomatic populations through mass screening programs (e.g., mammography, Pap test)
Tertiary prevention:
- Treatment of known cases by surgery, radiation, and chemotherapy or combination
- Pain-relieving palliative treatment