ECIS - European Cancer Information System

Glossary

Here are some definitions or explanations of specific terms and/or acronyms as they are used across the ECIS web-application.

Adjustment. A summarizing procedure applied to a statistical measure in which the effects of differences in composition of the populations being compared have been minimized by statistical methods.

Age-specific rate. An age-specific rate is the incidence or mortality rate for a specified age group, in which the numerator and denominator refer to the same age group; it is expressed as the number of new cancer cases or deaths per 100,000 population at risk. Five-year age categories are normally used (highest group 85+).

ASR (age-standardised rate). The ASR is a weighted mean of the age-specific rates where the weights are taken from the population distribution of a standard population; the ASR is expressed per 100,000. Comparison of rates referring to different time periods or different geographical areas is only possible after considering the differences in the age structure of the underlying populations. The age-standardisation allows the comparison of the rates that are arithmetically adjusted to have the same age structure of the standard population. The standard population used in the ECIS are the following old European Standard Population, new European Standard Population, and World Standard Population.

Crude rate. The crude rate is the ratio of the number of new cases or deaths in a specified population and time period to the size of the population at risk during the same time period. Incidence and mortality rate are usually presented as an annual rate per 100,000 persons at risk.

Cumulative risk. Cumulative incidence/mortality is the probability or risk of individuals getting/dying from the disease over a specified age-span. Cumulative risk is expressed as the number of cases/deaths per 1000 person-years that are expected to occur in a given population between the specified age limits (e.g. between birth and the age 84 years) if the cancer rates were as those observed in the specified time period in the absence of competing causes. Like the age-standardised rate, cumulative risk permits comparing between populations of different age structures.

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 (see age-specific rate and rate above). The rate provides an approximation of the average risk of developing a cancer in a population for the time period of reference.

Mortality. Mortality is the number of deaths occurring in a given period in a specified population. It can be expressed as an absolute number of deaths per year or as a rate per 100,000 persons per year.

Percentage change. The percentage change compares two age-standardised rates (ASR): the rate of the selected country with the rate of the selected reference (Europe or EU28). The formula is (ASRcountry-ASRreference)/ ASRreference.
For example, a relative change of +5% indicates that the country rate is 5% higher than the selected reference rate. Similarly, a relative change of -10% indicates that the country rate is 10% lower than the selected reference rate.

Population at risk. The part of a population which is susceptible to develop a specific cancer. It is defined on the basis of demographic data, such as place of residence, sex, age group, etc. Years of risk duration are counted in person-years.

Relative survival. The relative survival is a standard indicator for comparing cancer survival in population-based studies when the underlying cause of death in unknown. Relative survival is the ratio of the observed survival of patients to the expected survival in a comparable group in the general population for the same region, age, sex and calendar year. It can be interpreted as the survival probability of cancer patients in the absence of other causes of death, which can vary widely between countries. In the EUROCARE-5 study the expected survival was estimated by the Ederer II method from the lifetables of all causes mortality by age, sex, cancer registry and calendar year. Relative survival of patients diagnosed in 2000-2007 and followed up to 2008 was estimated using the classic cohort approach. Relative survival was standardised by age using the International Cancer Survival Standards (ICSS). The mean European relative survival was estimated by weighting country-specific relative survival by the country population.

Survival or Observed survival. It is the probability to survive after a given time from diagnosis (1,3, or 5-year), regardless from the cause of death. Observed survival probability is influenced by mortality due to cancer and to other causes of death. In international comparisons of cancer survival the effect of causes other than cancer, which can vary widely by countries, is removed by using relative survival.

 

References:

Greenland, Sander, et al. A Dictionary of Epidemiology. Vol. 6, edited by Miquel Porta, Oxford University Press, 2014.

https://seer.cancer.gov/cgi-bin/glossary/glossary.pl