epidemiology of cancer Flashcards
what did cristian tomasetti and bert volelstein say in an article
-some tissue types give rise to human cancer million times more often than any other tissues
-only a third of the variation in cancer risk among tissues is attribuable to enviromental factors and inherited dispositions
-basically a majority of cancers are due to bad luck arising during dna rep
what was the reaction of epidemiologists after berts claim
-they were like bro wtf
-the epidemiologists said that the claim was wrong
-cancer rates change over time
-a majority of cancers are preventable
true or false cancer rates are changing over time
-true
-different cancers in different tissues change over time
what was the data that bert was looking at when he made his claim
-he was looking at the r^2 value of 0.65
-a linear corrolation of 0.804 suggests that 65% of the differences in cancer risk between different tissues can be explained by the total number of stem cell divisions in those tissues
why was berts data kinda ass
-because his 65% of the differences in cancer risk between different tissues can be explained by the total number of stem cell divisions
-it can’t explain the differences in cancer risk between different people and between different populations
-does not explain hy colorectal cancer is so mugh higher in canada compared to other countries
what is epidemiology
study of patterns and causes of disease in a population
what does cancer surveillance in epi mean
-measures burden of disease, incidence and mortality trends
-who gets cancer
-how many get cancer
how many will die
-is the risk of getting cancer increasinf or decreasing
what does cancer risk mean in epi
assessing candidate etiologic factors
what does cancer prevention mean in epi
assessing the efficacy and the impact of screening, chemoprevention and other preventive approaches
what does cancer survival mean in epi
assessing prognostic factors and determinants of quality of life
what are the 4 main things that people in epi study
-cancer surveillance
-cancer risk
-cancer prevention
-cancer survival
measuring occurrence of cancer: number of cases
-new cancer cases
-new cancer deaths
-units: cases
-number of cases are useful for health system planning like how many beds you need in a hospital
What does incidence rate;
new cancer cases in a population per person years
what is the mortality rate
new cancer deaths in a population per person years
what are the units in epi
cases per person time
unlike number of cases, rates account for….
population size and time frame and so are useful for measuring risk and causality
why is the rate of cancer in 85ys old high than 60 years olds
because there are more 65 years olds but there are less 85yrs old. but there are more 85yrs old that have cancer
true or false; incidence rate of cancer is higher in high income countries
true
why is the rate of incidence is higher in high income countries
-better diagnosis in high income countries
-our heaqlth systems are better which help us escape easier deaths
what census is used in direct afe standardization
-2011 census population in canada (cross-time comparisons)
-1960 world population (cross-country comparisons)
what happens after direct age standardization
-all populations have the same standard age distribution
-any difference are not caused by age, basically everyone is 40
why is direct age standardization kind of a slay
allows comparing populations with different age structures (countries, time periods) to assess changes in cancer risk
what is crude incidence rate
dividing by population size adjusts for changes in pop size
is your risk of cancer increasing over time
it is decreasing
true or false: age standardized incidence rates in canadians are getting lower
-false, they are kinda equals out
-some are getting lower and some are getting higher
do we survive more
yeah we do
-that is due to less lung, colorectal and best cancer mortality
what are the odds to get cancer as a man and a woman
-44% in men
-43% in woman
what are the odds to die from cancer as a man and a woman
-26% in men
-22% in women
net cancer survival adjusts for….
competing causes of death
which is when people had cancer and they still end up dying
what is the rate of survuval for colorectal cancer
67%
what is the rate of survuval of prostate cancer
91%
what was the 5 year survival rate in the 40s vs now
-25%
-65%
true or false: childhood cancer incidence increased and morality decreases
true
why is the incidence rate of cervical cancer so different between southern afrika and australia
-less pap smears to detect pre cancer and cancer
-australia has more screenings
-hpv causes cervical cancer which can be prevented by protection
what are the causes of liver cancer
-hep c and b
-alcohol
why does mongolia has so much liver cancer
hep b is the most prevalent in mongolia due to unsanitary practices in the past
true or false: the dormant phase of tumor growth lasta 12 years
false: 15 years
when can you usually detect cancer
around 17yrs after onset
true or false; we saw directly after the people started to smoke more that there was a rise in lung cancer raters
false it took like 20 years before we fully saw the effects
what was the leading cancerin the us before lung cancer
-stomach cancer
stomach cancer is caused by what
-salt consumption
-ulcers caused by helicobacter pylori
why is stomach cancer less of a slay in the us now
People stopped using salt top preserve things
true or false: lung cancer used to be rare
true
when did people start to smoke more
-during the 1st world war soldiers were given rations
who was the lung cancer icon aka he coined the cancer was caused by tabacco
alton ochsner
why was the smoking rate lower in the 30s
there was the great depression
who was the doctor that said that lung cancer was not caused by smoking cigarettes
dr evarts graham he was like there is now was that smoking causes lung cancer
true or false; we can’t do an rtc in cancer research
true we can’t because it would be unethical to do that
why was there a drop in skoming in the 50s
two big papers said that cigarettes causes cancer but only doctors saw that literature
problems with clinical trials in research
-rtc are unethical
-not feasible to randomize exposure (ex: enviromental pollution)
-most individual cancers have lpw incidence, would need yto ramdomize large pop =$$$
-long induction+clinical period
-limited of comparisons can be made
what are analytical studies
-measures the association between an exposure (biological, behavioral, enviromental, medical, treatment) and a health outcome (cancer)
-includes a control group to compare outcomes
what is a counter factual
-what would have happened in absense of risk factor x
-in the case of lung cancer it would be risk factor; smoking
what is causal inference
-counterfactuals
-does risk factor x causes y
inferring causal effects problems
-we can’t really go back in time cuz we can;t control who smokes/smokes
-so in the case of lung cancer it is kinda impossible to put the blame on smokies
evarts graham and ernst wynder performed what in the 50s
-performed a famous case control study to refute the theory smoking=cancer
-recruited 684 cases of lung caner and 750 controls
what did graham and wynder learn in their iconic study
-we learned the outset of our study that the hospital records did not supply satisfactory asnwers to our questions, it was therefore decided to seek the disired information by special interviews
true or false: in case control studies you ask questions about if they were exposed to smth in the past
true
what si relatibe risk aka rr
-rr=1; exposed individuals have the same risk of experimencing the outcome as unexposed individuals
-rr> exposed individuals have a higher risk of experimencing the outcome as unexposed individuals
-rr<1; exposed individuals have lower chances of experimencing the outcome as unexposed individuals
caution rr is a measure of…
association (corrolation), not of causal effect (correlation is not causation)
risk of lung cancer in chain smokers and excessive smokers is …xhigher than none and light smokers
30x
what was the conclusion of grahams second case control study
-lung cancer is caused by smoking
what did graham died of
lung cancer lol
whjat did doll and hill discovered
-found the same as graham
-british dics study
-40 000 peeps
march 1954 linked responses with
death records
issues with observational data
-exposure may be correlated with other extraneous factors causing disease (confounding bias)
-how xab we know if the association we observe refelects a true fcausal relationship
-ex: does coffee cause cancer
does coffee cause cancer
-no lol but they corrolated people that smoke moire usually drink more coffee
-confounding: smoking
-coffee does not increase the risk of cancer mortality after adjusting for smoking
information bial
-error due to incorrect measurement of exposure and or health cancer
-ex: people said that they ate an apple a day while they did not
what is the causal agenbt of cervical cancer; histiry behind
-observations in the 1900s; cervical cancer is rare in nuns but freqyuent in sex workers and wives of husbands who frequent sex worker
-they did a case control study: cervical cancer cases ahd more remarriage, younger age. atmarriage, younger age at first pregnancy and more sex than the controls
-we thought it was herpes that causes cervical cancer in 60s and 70s
when did we say hov causes cervical cancer
1995 classified as a iarc; group 1 carcinogen
when was hopv detected in cervical cancer
1983
how were we able to coin hpv=cancer
thanks to pcrrr
non steroidal anti inflammatory drugs aka nsaids cause what
reduce inflammation and prevents blood clots and lowers the rate between 10-50% of colorectal cancer
low dose aspirtinb reduced risk of cancer by… and mortality by…
25% and 39%
what is population attributable fraction
-what proportion of cancer cases ate attributable to a specific exposure
-depends on rr; the more it increases the more paf increase
look over the rr graphs
ss
… of melanomas is caused by sunburns in youth
50%
what is cancer screening
-examination of asymptomatic people in order to identify disease or disease precursor
conditions for screenings
-must be pre clinical phase during which disease is undiagnosed, asymptomatic but detectable
-must be somne benefit of early treatment over later treatmeant
wjay is peak time to detect smth with screenings
9-17 years
COLORECTAL CANCER SCREEENING RESUKTS
-INTERVENTION GROUP HAD 23% lower colorectal cancer incidence and 31% lower colorectal mortality riskl
true or false: ovarian cancer is a slay
no
screening recommend:
-colorectal
-cervical
-lung
-breast
what is the cabnadian task force on preventiver heralth cate
evaluates syustematic review evidence to devlop consensus recommendations to rpeventivbe interventiopm
screening is mot revcommended:
-pelvic exams for other gyni cancers
-prostare canecrt
