Presentation on theme: "Cancer epidemiology Epidemiology & public health – understanding and control of disease at population level The scientific basis – knowledge through probability."— Presentation transcript:
Cancer epidemiology Epidemiology & public health – understanding and control of disease at population level The scientific basis – knowledge through probability Describe problems Investigate hypotheses Monitor control
Epidemiology reveals causes Time, place and person Did exposure cause cancer? Was cancer caused by exposure?
Incidence New cases Not just deaths At what age? Is it changing?
prevalence Current patients – and current cured? The patient pathway Including communication and palliative care Health services activity = social cost Drug treatment – prevalence more valuable than incidence
Individual and environment Why did I / she get this disease? Interaction of organism with exposure A probabilistic event … Both direct exposure and trigger…
Risk / Probability Individual risk - of getting disease Population probability – of getting disease Attributable risk – for a factor causing disease Population attributable risk = attributable risk x exposures
established risk factors for some cancers: Tobacco smoking (lung, throat, pancreas, stomach, bladder.., Alcohol (mouth, throat, food pipe, breast, liver) Ultraviolet light (skin) Lack of exercise (bowel) High fat, low fruit and vegetable diet (bowel) Obesity (breast, bowel, womb) The following have not been confirmed or have been disproved: Deodorant Underwired bras Cuts and bruises Make-up Risks and low risks
Childhood cancers: case-control study Setting and subjects: Maps of emissions of many different substances were published on the internet by the National Atmospheric Emissions Inventory and "hotspots" for 2001 were translated to map coordinates. Child cancer addresses were extracted from an earlier inquiry into the carcinogenic effects of obstetric radiographs; and their postcodes translated to map references. Main results: Significant birth proximity relative risks were found within 1.0 km of hotspots for carbon monoxide, PM10 particles, VOCs, nitrogen oxides, benzene, dioxins, 1,3-butadiene, and benz(a)pyrene. Calculated attributable risks showed that most child cancers and leukaemias are probably initiated by such exposures Knox EG Journal of Epidemiology and Community Health 2005; 59: 101-105
Epidemiological knowledge Non-experimental Not truth but probability Looking for confounding
Criteria 1.Temporal relationship Value of prospective designs
Criteria 2.Plausibility Working with biologists From animals to humans
Criteria 3.Statistical association Note the type of statistics used -
Criteria 4.Dose relationship children/adults Easy to do in laboratory, difficult to determine in epidemiology eg. use distance for chronic exposures
Criteria 5.Specificity Attributable risk lung cancer – 90% from smoking childhood leukaemia ~ 25% from exhausts, ~ 6% medical radiation <1% from Necessary but not sufficient potential viral trigger of cancer cell clone
Criteria 6.Consistency / repeatability Exposures, populations The world as laboratory ….
Canadian Medical Association J. April 3, 2001; 164 (7) Integrated oncology - cervical cancer
Control - surveillance Statistics as vital statistics
Survival Prognosis for patient and doctor Performance of services
Lung & colorectal cancers 5- year relative survival Selected health authorities and England total LungColorectal % Dorset5.556 Oxfordshire5.247 Kensington8.948 Tees2.826 Sunderland2.633 England5.543