Epidemiology of cancer Flashcards
All cancers combined, what is their ranking in terms of causes of death western countries?
second
How has cancer mortality in western countries changed from the 60s?
It is decreasing, completely different in low income countries
How has mortality from CVDs changed in western countries?
decreased
What is important to not about the epidemiology of cancer?
CANCER MORTALITY CHANGES WITH TIME AND VARIES DEPENDING ON GEOGRAPHICAL LOCATION
What can affect mortality rates?
Access to healthcare, effectiveness of therapy
What can affect incidence?
Incidence rates reflect causality – they reflect risk factors and lifestyle
What are the most common cancers in men and women?
women: breast
men: lung and prostate
distribution around the world varies though
Geographical distribution of melanoma
- For melanoma, there is almost a 200:1 ratio for incidence in Australia compared to that in China
- Melanoma is often related to UV light (sun exposure is increased in Australia)
- Additionally, in Australia, genetics play a role because UV light is more damaging in people with fair skin
- A large proportion of deaths in Australia are attributable to melanoma
Geographical distribution of prostate cancer
- 75:1 ratio for incidence in North America compared to that in China
- The incidence is increasing in China, so this ratio will reduce over time
- Prostate cancer is detected by looking at PSA levels
- PSA is measured in a large proportion of men over the age of 55 in high income countries
- Prostate cancer is more likely to be detected in North America (perhaps many silent cases in China)?
Geographical distribution of lung cancer
- In lung cancer, the ratio between Eastern Europe and Western Africa is still relatively high
- The vast majority (85-90%) of lung cancers are due to tobacco smoke
- Smoking prevalence is increasing in Africa
Why is measuring incidence better than measuring mortality to assess trends?
For non-lethal cancers, there is a big gap between incidence and mortality; therefore incidence is a better way to measure trends in different countries. We use incidence to study causality and generate a hypothesis.
What can migrant studies be used for?
We can discover whether genetics and environmental causes contribute to cancer development.
- Following migration a rapid change in risk implies that lifestyle/environment factors act important
- A slow change in risk suggests that exposures early in life are the most relevant
- Persistence of rates between generations suggests genetic susceptibility is important in determining risk
Give an example of cancers that are affected by the environment through a migrant study
- The Japanese migrated to the USA
- The Japanese that remained in Japan have a very high incidence of stomach cancer
- The incidence of stomach cancer in white Americans is very low
- The Japanese that migrated developed a much lower incidence rate – more similar to that seen in Americans
- This was seen in the first generation, and even more so in the second generation.
- The opposite happened with colon cancer
- Colon cancer is rare in Japan and common in the USA. Japanese migrants developed a greater risk of developing colon cancer
- This suggests that cancer is heavily influenced by environmental causes
How have the rates of stomach cancer and lung cancer changed over the years?
There has been a very steep increase in lung cancer over the years, and a decrease in stomach cancer.
Describe the trend in mortality and incidence of cancer in high and low income countries
In high-income countries, we are observing a plateauing of incidence rates. Mortality rates are decreasing in high-income countries (the picture in low-income countries is completely different). This same trend, in high-income countries, is seen in both males and females.
