GLOSSARY OF TERMS

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 ASR below). The rate provides an approximation of the average risk of developing a cancer.

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.

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. 

Age-specific rate
The age-specific rate is calculated simply by dividing the number of new cancers or cancer deaths observed in a given age category during a given time period by the corresponding number of person years in the population at risk in the same age category and time period. For cancer, the result is usually expressed as an annual rate per 100,000 person-years. In ITACAN, five-year age categories are used (highest group 85+).

Crude rate
Data on incidence or mortality are often presented as rates. For a specific tumour and population, a crude rate is calculated simply by dividing the number of new cancers or cancer deaths observed during a given time period by the corresponding number of person years 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)
An age-standardised rate (ASR) is a summary measure of the rate that a population would have if it had a standard age structure. Standardisation is necessary when comparing several populations that differ with respect to age because age has such a powerful influence on the risk of cancer. The ASR is a weighted mean of the age-specific rates; the weights are taken from population distribution of the standard population. The most frequently used standard population is the World Standard Population. The calculated incidence or mortality rate is then called age-standardised incidence or mortality rate (world). It is also expressed per 100000. The European standard is often used and ITACAN gives the possibility of also choosing a Italian standard where the age-distribution is from the Italian population in 2000.

Age distributions of the standard populations used for age standardisation in ITACAN (per 100,000)
Age group World
ASR (W)
European
ASR (E)
Italian
ASR (I)
0-4 12000 8000 5900
5-9 10000 7000 6600
10-14 9000 7000 6200
15-19 9000 7000 5800
20-24 8000 7000 6100
25-29 8000 7000 6800
30-34 6000 7000 7300
35-39 6000 7000 7300
40-44 6000 7000 7000
45-49 6000 7000 6900
50-54 5000 7000 7400
55-59 4000 6000 6100
60-64 4000 5000 4800
65-69 3000 4000 4100
70-74 2000 3000 3900
75-79 1000 2000 3500
80-84 500 1000 2400
85+ 500 1000 1900
Total 100000 100000 100000

Cumulative risk
Cumulative incidence/mortality is the probability or risk of individuals getting/dying from the disease within a specified age interval within a time period. For cancer and from age 0, it is expressed as the number of new born children (out of 100) who would be expected to develop/die from a particular cancer before the age of 75, 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.

Standard error
The standard error of a rate is a measure of the sampling variability of the rate.

Confidence interval
A range of values that has a specified probability of containing the unknown true rate or trend. The 95% (p-value = .05) and 99% (p-value = .01) confidence intervals are the most commonly used.

Estimated annual percentage change (EAPC)
The estimated annual percentage change is used to describe the magnitude of change in the trend on fitting a simple regression model to the log of the ASR. It is the average annual rate of change in the ASR over the time period selected.
Survival
Cancer survival statistics are typically expressed as the proportion of patients alive at some point subsequent to the diagnosis of their cancer. Relative survival is an estimate of the percentage of patients who would be expected to survive the effects of their cancer. Observed survival is the actual percentage of patients still alive at some specified time after diagnosis of cancer.
Survival of cancer patients in Italy
Prevalence
Cancer prevalence is defined as the number or percent of people alive on a certain date in a population who previously had a diagnosis of the disease. It includes new (incidence) and pre-existing cases, and is a function of both past incidence and survival.
Cancer prevalence in Italy

ITACAN, 2014 AIRTUM.