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Glossary of terms

Cancer Registry

The cancer registry has a pivotal role in cancer control. Its primary function is the maintenance of a file or register of all cancer cases occurring in a defined population in which the personal particulars of cancer patients and the clinical and pathological characteristics of the cancers, collected continuously and systematically from various data sources, are documented. The registry analyses and interprets such data periodically and provides information on the incidence and characteristics of specific cancers in various segments of the resident population and on temporal variations in incidence. Such information is the primary resource not only for epidemiological research on cancer determinants but also for planning and evaluating health services for the prevention, diagnosis and treatment of the disease. (Cancer Registration: Principles and Methods IARC Scientific Publication No. 95).

Incidence

Incidence is the number of new cases arising in a given period in a specified population. This information is collected routinely by cancer registries. It can be expressed as an absolute number of cases per year or as a rate per 100,000 persons per year. The rate provides an approximation of the average risk of developing a cancer.

Population at risk

The population at risk includes all individuals susceptible to a specific cancer. It is defined on the basis of demographic variables, such as place of residence, sex, age group and (where appropriate) ethnicity.

Crude rate

Data on incidence are often presented as rates. For a specific tumour and population, a crude rate is calculated by dividing the number of new cancers observed during a given time period by the corresponding number of people in the population at risk. For cancer, the result is usually expressed as an annual rate per 100,000 persons at risk.

ASR (age-standardised rate or age-adjusted rate)

An age-standardised rate (ASR) is a summary measure; it is the rate that a population would have if it had a standard age structure. Standardization is necessary when comparing several populations that differ with respect to age structure, because age has a powerful influence on the risk of cancer. The most frequently used standard population is the World standard population. The calculated incidence rate is then called the World Standardised incidence Rate. It is also expressed per 100,000. The World standard population used in this application is as proposed by Segi (1960) and modified for the first volume of the series by Doll and al. (1966).

Age distribution of the world standard population used for age standardization in CI5

Cumulative rate

Cumulative incidence is the probability of individuals getting the disease during a specified period. For cancer, it is expressed as the number of newborn children (out of 100, or 1000) who would be expected to develop a particular cancer before the age of 75 or (80 or 85) if they had the rates of cancer observed in the period, in the absence of competing causes. Like the age-standardised rate, it permits comparisons between populations of different age structures.

Useful links

• The International Agency for Research on Cancer IARC (IARC)
• The Cancer Surveillance Branch at IARC
• The World Health Organization (WHO)
• The International Association of Cancer Registries (IACR)
• The Union for International Cancer Control (UICC)

Aknowledgements

Cancer Incidence in Five Continents (CI5) is the result of a long collaboration between the International Agency for Research on Cancer and the International Association of Cancer Registries. The publications provide data on cancer incidence collected by population-based cancer registries over more than fifty years, and the contents of this collected edition represent the results of this effort. Their work deserves gratitude not only from investigators who use the information they provide, but also from all those who may benefit from the increase in our knowledge of cancer patterns and trends.

We would like to recognize and acknowledge also the work of the past editors who were involved in collecting, evaluating and preparing the data appearing in one or more of the 12 volumes of CI5. Particular thanks are due to the late Sir Richard Doll, who was in large measure responsible for bringing to fruition the idea of creating a source of comparable international data on cancer incidence for the purposes of research into cancer cause and prevention.