The study of cancer epidemiology uses epidemiological methods to find the cause of cancer and to identify and develop improved treatments. Observational epidemiological studies show associations between risk factors and specific cancers which mostly serve to generate hypotheses about potential interventions that could reduce cancer incidence or morbidity. This area of study must contend with problems of lead time bias and length time bias. Lead time bias is the concept that early diagnosis may artificially inflate the survival statistics of a cancer, without really improving the natural history of the disease. Randomized controlled trials then test whether hypotheses generated by epidemiological studies and laboratory research actually result in reduced cancer incidence and mortality. In many cases, findings from observational epidemiological studies are not confirmed by randomized controlled trials. This session discusses more about cancer epidemiology.