Cancer 11: Epidemiology of Cancer Flashcards
Relation between incidence and mortality in cancer
- sometimes there is high incidence and low mortality in cancers that are not lethal
- if incidence and mortality are very close the cancer is very lethal (e.g. pancreatic cancer and some acute leukemias)
What are the most common causes of death?
- cardiovascular disease
- cancer (all cancers collectively)
- other
What affects incidence and mortality?
Prevention affects incidence.
Treatment affects mortality.
MIgrant studies
- Extent and rate of change that are informative
- A rapid change in risk following migration implies that lifestyle/environment factors act late in carcinogenesis
- A slow change suggests that exposures early in life are the most relevant
- Persistence of rates between generations suggests genetic susceptibility is important in determining risk
=> allows to see if genetic or environmental factors are more important in developing the cancer.
Why did the incidence of stomach cancer decline over the last decades?
-> Refrigerators
Better storage of food -> less bacteria (H. pylori) -> less stomach cancer
Stomach cancer is caused by environmental factors, not inherited.
How has the incidence of cancer changed in the western world?
- it was increasing but has now plateaued.
- This could be due to a development in diagnostic tools, detect cancer in earlier stages.
- Some of the incidence is due to PSA screening and mammography.
- Exposure to risk factors is another reason (e.g. less smoking)
How has mortality due to cancer changed?
- it has decreased
- this is due to better therapies
- this is also due to better screening and detecting cancer at earlier stages -> more curable.
Incidence, Mortality and Burden of cancer - Summary
- 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) – effects of earlier diagnosis, screening, changes in risk factors?
- Mortality is decreasing in most high-income countries (e.g. -23% between 1990 and 2008 in US men), not in low income countries
- Total burden is increasing because of demographic changes (ageing populations, increasing size), and Westernisation of lifestyles
Success rate for treating leukaemia in children?
- 80-90% in the western world
- in poor countries this is lower because they don’t have access to the treatments necessary.
How are high and low income countries different epidemiologically?
- low income countries are still in the epidemiological transition
- more infection based cancers.
- no screening
- less access to more effective strategies
What are some hereditary conditions that lead to cancer?
- hereditary retinoblastoma -> retinoblastoma
- xeroderma pigmentosum -> skin cancer (they cannot repair the damage, they need exposure to sunlight to develop cancer)
- Wilm’s tumour -> kidney
- Familial adenomatous polyposis -> colon, rectum cancer
- Paget’s disease of bone -> bone
- Fanconi’s aplastic anaemia -> leukemia, liver, skin
- Li-Fraumeni syndrome -> sarcomas, brain, breast, leukemia
What are the main RFs for cancer?
Smoking : 29-31 Diet : 20-50 Alcoho: 4-6 Infection: 10-20 Occupation: 2-4 Reproductive hormone: 10-20
Smoking as a RF for cancer
Smoking accounts for at least 30% of all cancer deaths
Smoking is associated with increased risk for at least 15 types of cancers
Smoking causes 90% of lung cancer deaths in men and 80% in women
RFs for colorectal canccer
- red meat
- you should eat fibre from fruit and veg
Alcohol as a RF for cancer
- Oral cavity, pharynx, larynx, oesophagus, liver
- all types of alcohol
- mechanisms poorly understood
- synergism with tobacco
- balance with preventive effect for CHD
Obesity and cancer
- obesity is a RF for cancer
- obesity is an inflammatory disease
- Many inflammatory cytokines, there is chronic inflammation which is one of the hallmarks of cancer.
Guidelines for dietary prevention of cancer
- Be as lean as possible without becoming underweight;
- Be physically active for at least 30 minutes every day;
- Avoid sugary drinks. Limit consumption of energy-dense foods (particularly processed foods high in added sugar, or low in fibre, or high in fat);
- Eat more of a variety of vegetables, fruits, wholegrains, and pulses such as beans. Basing our diets on plant foods, which contain fibre and other nutrients, can reduce our risk of cancer;
- Limit consumption of red meats (such as beef, pork and lamb) and avoid processed meats. To reduce your cancer risk, eat no more than 500g cooked weight (700-750g uncooked) per week of red meats, like beef, pork and lamb, and avoid processed meat such as ham, bacon, salami, hot dogs and some sausages;
- If consumed at all, limit alcoholic drinks to 2 for men and 1 for women a day;
- Limit consumption of salty foods and foods processed with salt (sodium);
- Don’t use supplements to protect against cancer. To reduce your risk of cancer, choose a balanced diet with a variety of foods rather than taking supplements.
Westernisation of lifestyle and cancer
Western Lifestyle:
- Energy dense diet, rich in
- fat,
- refined carbohydrates - animal protein
- fat,
- Low physical activity
- Smoking and drinking
Consequences:
- Greater adult body height - Early menarche - Obesity - Diabetes - Cardiovascular disease - Hypertension
Name some pathogens and what cancers they can cause. How much cancer is due to infections?
HPV (16,18) -> Cervix, Head and Neck
EBV -> Hodgkin’s Lymphoma, Burkitts
HCV, HBV -> Liver
H. Pylori -> Stomach
~16% cases of cancer likely caused by infectious agents worldwide
25% in Africa
<10% in Europe (1 in 33 in UK)
Key Points
- Cancer is a leading cause of death
- The epidemiology of cancer tells us that cancer incidence is related to:
Age
Common environmental causes
Geographical variation and secular trends
There are several well defined risk factors for cancer, including smoking, diet and alcohol consumption. - The process of carcinogenesis is important in understanding the development of cancer. Important factors involved in this process include chemical carcinogens, radiation and oncogenic viruses
- Inherited / familial cancers are rare, but have provided valuable information in understanding the process of carcinogenesis.
