ABSTRACT
Introduction Cancer epidemiology studies the distribution of cancer in populations and its changes over time and looks at characteristics of different population groups, not only those who get the disease but also those who do not, to find out how these groups differ. It evaluates the associations between different exposures and diseases to decide whether the observed relationships are likely to be causal. Its ultimate goal is to identify risk factors that may lead to the introduction of effective preventive measures. Although cancer epidemiology is not a new science, it has matured only in the last half of the 20th century, when communicable diseases underwent a sharp and sustained fall. The development and growth in the field of vital statistics made it possible to study the patterns of cancer mortality. Unfortunately, mortality data published nowadays by the World Health Organization (WHO) are of different quality and may have several biases:
■ coverage of the population is incomplete as mortality rates are implausibly low in some countries
The need for more accurate data on cancer patients and the relatively clearcut pathological case confirmation led to the development of hospital-and population-based cancer registries.
