Glossary

Age-specific rate: the rate for a specific age-group. The numerator and denominator relate to the same age group.

Age-standardisation: a method of removing the influence of age when comparing populations with different age structures. This is usually necessary because the rates of many diseases vary strongly (usually increasing) with age. The age structures of the different populations are converted to the same ‘standard’ structure; then the disease rates that would have occurred with that structure are calculated and compared.

Cancer: refers to a large range of diseases in which some of the body’s cells become defective, begin to multiply out of control, can invade and damage the area around them, and can also spread to other parts of the body to cause further damage.

Cancer incidence:  the number of new cancers diagnosed during a specified time period (usually one year).

Cancer mortality: the number of deaths occurring during a specified time period (usually one year) for which the underlying cause of death is cancer.

Cohort method: a method for calculating survival. It follows a group (cohort) of patients all diagnosed in a specified era, e.g. 2005–2009, and calculates the proportion of the original cohort that is still alive after a specified period of time after diagnosis, e.g. 5 years. Compare to the period method.

Crude rate: the number of events in a given period divided by the size of the population at risk in a specified time period.

Period method: a method for calculating survival. It specifies a period of time, e.g. 2010–2014, and calculates survival based on all patients who live part or all of their post-diagnosis life during that period. Compare to the cohort method.

Prevalence: the number of people alive with a prior diagnosis of cancer at a given time. The longest period for which it is possible to calculate prevalence using the available national data (from 1982 to 2016) is currently 34 years so this is used to provide an estimate of the ‘total’ prevalence of cancer as at the end of 2015, noting that people diagnosed with cancer before 1982 are not included.

Relative survival: the ratio of observed survival of a group of persons with cancer to expected survival of those in the corresponding general population after a specific interval (such as 1, 3 or 5 years) following diagnosis.

Stage: the extent of a cancer in the body. Staging is usually based on the size of the tumour, whether lymph nodes contain cancer, and whether cancer has spread from the original site to other parts of the body.

Survival: a general term indicating the probability of being alive for a given amount of time after a particular event, such as diagnosis of cancer.