3: Cancer Epidemiology

Question 1

Incidence?

Answer 1

Incidence is increasing for common cancer sites in both high-income (now with plateauing and even decreases) and low-income countries (e.g. breast, colorectum, prostate) – possibly due to effects of earlier diagnosis, screening, changes in risk factors?

Question 2

Discuss the epidemiological evidence for cancer causation

Answer 2

Epidemiology shows cancer is related to:

• Age
• Common environmental causes
• Geographical Variation and secular (religious) trends

Question 3

Summarise incidence/mortality rates in high/low income countries

Answer 3

HIGH income countries (e.g. Europe, US, Canada)

• Incidence = Increasing but plataeuing (e.g. breast, prostate, colorectal)
• Mortality = Decreasing due to earlier diagnosis and better treatments

LOW income countries (e.g. Africa, China)
- BOTH incidence + mortality INCREASING

TOTAL BURDEN = INCREASING due to demographic changes (ageing population, increasing size) and Westernization of lifestyles

Question 4

Top 5 countries with highest incidence rates?

Answer 4

1. Ireland
2. Belgium
3. France
4. USA
5. UK

Question 5

Main geographical variation of cancers

Answer 5

Prostate/breast - N. America
Melanoma - Australia/NZ
Lung - East Europe
Colorectal - Japan
Esophageal/Liver - China
Bladder - South Europe

Question 6

Discuss the epidemiological evidence for cancer causation

Answer 6

• Japanese have high incidence of stomach cancer (1970s) whereas US whites had low incidence
• Japanese migrated to Hawaii
• Hawaii-Japanese people had greater incidence than Hawaii-Caucasians
• Suggests there is genetic factor to cancer causation

Question 7

What is the correct way to measure cancer trends in ageing population?

Answer 7

Need to consider incidence/mortality RATE, not just incidence.
Divide incidence/mortality by population number

Question 8

Risk of smoking in cancer?

Answer 8

30% of ALL cancer deaths

90% lung cancer deaths in men, 80% in women

Question 9

Role of dietry fibre in colorectal cancer?

Answer 9

Dietry fibre lowers risk of colorectal cancer

Question 10

Infectious agents and cancer

Answer 10

Around 16% of cancer worldwide likely caused by infectious agents

25% in Africa
<10% in Europe

HPV -> Cervical cancer
Hep B/C -> Liver cancer
H. Pylori -> Stomach cancer