Lecture 2 Flashcards

Question

How do we measure the incidence of cancer?

Answer 1

1. Risk 2. Odds of disease 3. Incidence Rate

Answer 2

No. of new cases in population over time / population initially at risk

Answer 3

No. of new cases in population over time / No. of people who remain disease-free

Answer 4

No. of new cases in population over time / total person-time at risk

Answer 5

Population is stable throughout period of disease is rare

Answer 6

Rate estimated without direct measure of person-time at risk

Answer 7

Population at mid-point of calendar period of interest x length of period

Answer 8

how much more likely the exposed group is to develop cancer than the unexposed group (collectively called measures of relative risk)

Answer 9

Risk in exposed / risk in unexposed

Answer 10

odds in exposed / odds in unexposed

Answer 11

incidence rate in exposed / incidence rate in unexposed

Answer 12

1.0 = no assocation greater than 1.0 = positive association (increased risk amoung exposed) less than 1.0 = negative association (decreased risk among those exposed)

Answer 13

to indicate how many extra cases the exposure is responsible for (assumes causality)

Answer 14

Risk difference (excess risk) = risk in exposed - risk in unexposed

Answer 15

evaluating the impact of introducing or removing a risk factors

Answer 16

assess how much disease incidence can be attributable to the exposure

Answer 17

Population attributable risk = excess risk x proportion of population exposed to risk factor (percentage)

Answer 18

measure of how much disease is attributable to a risk factor e.g. 84% of lung cancer incidence is attributable to smoking indicator of how many cancer cases could be prevented if risk factor removed e.g. 84% of lung cancer cases could be prevented if nobody smoked

Answer 19

looking at how much of cancer incidence is due to environmental factors or genetics

Answer 20

Breast and ovarian cancer syndrome (mutations in BRCA 1 & BRCA2) accounts for ~5% breast & ~5% ovarian cancers Li-Fraumeni syndrome (mutations in TP53) high risk of breast & bone cancer, leukaemia, & sarcoma Familial adenomatous polyposis (FAP) (mutations in APC) accounts for ~1% of bowel cancers Lynch syndrome / Hereditary non-polyposis colon cancer (HNPCC) (mutations in MLH1, MSH2, MSH6, and PMS2) accounts for ~3% of bowel cancers

Answer 21

Hereditary and non-hereditary forms Age at onset Risk in families Time trends International trends / migration

Answer 22

- In 1994 the BRCA1 gene was identified, that when mutated appeared to be responsible for most hereditary breast cancers - About 5% of all breast cancer cases are hereditary, with around half of those resulting from mutations in BRCA1 or BRCA2 - these mutations are rarely seen in nonhereditary form of breast cancer, suggesting the genetic pathways or mechanisms operating in the inherited and non-inherited cases are different - also been estimated that the lifetime risk of breast cancer in women with BRCA1 or BRCA2 mutations ranges from 50-85%, compared to 12% in the general population

Answer 23

Retinblastoma in childern 40% = bilateral, familal (occures soon after birth) 60% = unilateral, nonfamillal (occurs throughout early childhood) when a disease occurs in both genetic and nongenetic forms, the genetic form develops at much earlier ages that the nongenetic form This is because the non genetic form requires the accumulation of environmental exposures that only build up over time Consequently it takes longer for these diseases to develop

Answer 24

Concordance in 1st degree relatives suggets genetic component and concordance in spouses suggests environmental exposure as they aren't genetically linked

Answer 25

probability that a pair of individuals will both have disease, given that one of the pair has the disease

Answer 26

Two types = monozygotic share 100% genetic and dizygotic share 50% genetic If we look at then occurrence of disease in identical twins, there are 4 possibilities: Both twins have disease, or both do not have disease – these are the concordant pairs It is also possible that one twin has the disease and the other does not – these are the discordant pairs If identical twins are concordant, what does this tell us? Could the disease be genetic? YES – twins have identical genetics Could the disease by environmental? YES – similar exposures If identical twins are discordant – this suggest the disease is mainly environmental in origin

Answer 27

A pairs – both twins have disease D pairs – neither twin has disease B & C pairs – one has disease, one does not Now, most twins will be in category D (neither diseased), so we can ignore those, and look at the other 3 cells of the table We simply calculate the concordance rate as a / a+b+c

Answer 28

Increasing or decreasing trends in incidence over (short) period of time could mean environmental factors implicated Genetic characteristics do not change quickly

Answer 29

Gastric cancer incidence and mortality Migrant studies If a person moves from Japan to US, what happens to their cancer risk? Risk remains high over time = primarily genetic Risk lowers over time = primarily environmental

Answer 30

increasing availability of data on molecular subtypes of cancer (some even recorded in cancer registry data) The Human Genome Project. the creation of genome-wide databases of common genetic variations in humans has provided the foundation to more comprehensively examine genetic variations in relation to cancer risk

Lecture 2 Flashcards

Risk factors and cancer incidence (54 cards)