Lecture 6: Introduction to cancer Flashcards
what does the global burden of disease study show?
- combined male and female data
- shows years of life lost, measures health loss from early death
- provides a measure of the impact of the health conditions
- figure represents leading causes of life loss
what does this show?
leading causes of life loss
lung cancer is a leading cause of years of life lost. in 1990 it was ranked 17th, 14th in 2007, 12th in 2017.
what this show?
a figure representing burden of DALYs
- shows the leadings causes of DALYs for females
- breast and lung cancer have increased in the rank of DALYs overtime
whats this?
DALYs for males
- shows that lung cancer, stomach cancer and liver cancer all contribute significantly to DALYs for males
whats this?
number of DALYs by condition group and sex, 2006
cancer is leading cause of health loss estimates
what are the most important cancers for male DALYs?
- lung, bowel and prostate cancer are leading cancers for DALYs
what are the most important cancers for females DALYs?
- breast, lung and bowel cancer are most important for female DALYs
how can the public health model help with cancer?
Epidemiology is only source with scientific evidence of exposure and prevention
Need to know how common a disease is and does it play by the person, place or time.
Identify risk factors and protective factors.
How common/less common is it
what is the story about chimney sweeps and scrotal cancer?
- is an example of early cancer investigations.
- Observational descriptive cancer research
found that in england, ~1700s there was an occupational exposure of young boys being chimney sweeps, and it was found that the outcome of this was scrotal cancer!
however, in germany chimney sweeps whore tighter full-body clothing and these boys didn’t have as rates of scrotal cancer as high in england
what is the story about this cancer?
a doctor found many cases of kids with tumours in their jaws… it was often associated with another tumour somewhere in their body
- it was described as an ‘unknown lymphoma
- incidence was 18 per 100,000 children per year
- occurance was 6 months to 14 years- peak at 5-6 years
- more common in boys
- it was later discovered that it was not a new cancer, but a form of epstein bar virus - burkitt’s lymphoma
- was common in africa
what this show?
increase in lung and bronchus cancers in 1930-1990, but started to decrease after 1990.
- likely due to increased smoking rates in males during war times
what this shows?
females didn’t have us much of an increased death by lung and bronchus cancer as males.
the increase also took place from mid 1960s to 1990s+
- this is likely to be because females took up smoking a lot later than males did
why are case control studies better for cancers?
- cancers are rare outcomes
- RCTs wouldnt be ethical
- long periods between exposure and outcome
- would need to follow people up for long periods of time
- not efficient
what is an example of a case-control study for cancer?
‘Smoking and carcinoma of the lung”
published in the british medical journal, 1950
what is an example of a cohort study for cancer?
“the mortality of the doctors in relation to their smoking habits”
- published in britsih medical journal, 1954
what is cancer?
unregulated proliferation of cells
a breakdown in the processes which controls cell proliferation, differentiation, death of cells
how do you defince cancer growth and invasion?
- cancer is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues
- cancer cells can spread to other parts of the body through the blood and lymph systems. it can also spread across potential spaces in the body
- cancer is not just one disease but many diseases. there are more than 100 different types of cancer
- most cancers are named for the organ or type of cell which they start in
what is the progression of cancer?
most solid tumours arise in areas of hyperplasia
1) hyperplasia: increased local tissue size due to abnormal cellular proliferation
2) dysplasia: abnormal cell architecture
3) carcinoma in-situ: very abnormal cells, like cancer
4) invasion: abnormal cells invade the underlying tissue
5) metastisis: migration of cancer cells from the primary tumour to distant sites in the body, and development of secondary tumours at those sites
what are the cancer types?
- carcinoma
- sarcoma
- leukaemia
- lymphoma and myeloma
- CNS cancers
- benign tumours (not cancerous)
- malignant tumours (cancerous)
what are some key things to consider about the development of cancer?
- inherited predisposition of <5% of all cancers
- epigenetic mechanisms and direct DNA damage occurring as a result of environmental exposures are responsible for the development of the great majority of cancer
- usually a long time from exposure to cancer developing
- can be 15-40 years
- cancer is usually a rare complication of a common exposure
what are common causes of cancer?
- genes
- environmentsl
- chemical
- infectious agents
- lifestyle (diet, physical activity, body)
- occupation
what is primary prevention?
aims to prevent disease from ocurring, to reduce incidence
what is secondary prevention?
aims to improve outcomes in people who have developed disease, to reduce morbidity and mortality
what is teritary prevention?
aims to reduce number or impact of complications of disease
what is screening?
- aims to improve outcome, usually to reduce mortality
- there are screening programmes vs opportunistic screening
- all screening programmes do harm, some can do good as well
- screening is a pathway, not a test!
what is the screening pathway?
what is the criteria for assessing screening programmes?
- the condition is suitable for screening
- there is a suitable test
- there is an effective and accessible treatment or intervention for the condition identified through early detection
- there is high quality evidence, ideally from randomised controlled trials, that a screening programme is effective in reducing mortality or morbidity
- the potential benefit from the screening programme should outweigh the potential physical and psychological harm (caused by the test, diagnostic procedures and treatment)
- the health care system will be capable of supporting all necessary elements of the screening pathway, including diagnosis, follow up and programme evaluation
- there is consideration of social and ethical issues
- there is consideration of cost-benefit issues
what are some NZ national screening programmes?
- breastscreen aotearoa
- national cervial screening programme
- national bowel screening programme
what are DALYs?
DALY is made up of the sum of the years of life lost due to premature mortality + years of healthy life loss due to disability
