Guidance

Cancer registration methodology

Published 25 August 2021

Applies to England

Introduction

This document provides the methodology for the Cancer registration statistics for England publication produced by the National Cancer Registration and Analysis Service (NCRAS) within Public Health England (PHE). The Cancer registration statistics for England is an annual publication that reports on the number and rate of new cancer registrations and deaths due to cancer in England and includes sub-national geographies. The numbers and rates are broken down by cancer site, socio-economic status, sex and age group for all malignancies. For selected cancers, the number and rate of new registrations by stage at diagnosis are also reported.

The summary guide explains what the registrations statistics should be used for and who uses them. The data used in the Cancer registration statistics is part of the National Cancer Registration Dataset and is subject to the Quality assurance of administrative data.

To increase the timeliness of the cancer registration statistics, NCRAS may publish 2 releases. A ‘first release’, based on provisional data, will contain a summary of counts and rates of cancer diagnoses for the registration year for England only. The full analysis of cancer registrations including stage at diagnosis, based on finalised data, will then be published within another 6 months, and will contain data for regions of England. If the time to having the finalised data is within 3 months, or there is a significant delay to registering provisional data the full analysis only will be published. There may be small differences in estimates provided between the first and final release that arise from the finalisation process.

All publications consist of data tables and an accompanying bulletin. The data tables are produced in OpenDocument Spreadsheet format (.ods) and the bulletin is produced in html format to ensure accessibility. The most recent National Statistics Cancer registrations statistics for England can be accessed on the cancer registration statistics collection page.

Methodology

All cancers are coded using the International Classification of Disease 10th Revision (ICD-10). ICD-10 coding for cancer is based on the nature and anatomical site of the cancer. In the cancer registration statistics publication, the term ‘invasive cancer’ is used to refer to all invasive tumours (C00 to C97 in ICD-10 coding), excluding non-melanoma skin cancers (NMSC) (ICD-10 C44). Although NMSC is very common, the available figures are known to be under-estimates and unreliable for comparison purposes. This is because the policies and practices for the recording of NMSC have varied among the cancer registries over time. Time series for cancer registrations are published with and without NMSC. This provides users with consistent and meaningful statistics over time. The Cancer registration statistics publication also report on selected benign tumours (ICD-10 D32 to D33 and D35.2 to D35.4), all in situ tumours (D00 to D09) and tumours with uncertain or unknown behaviour (D37 to D48).

Cancer Incidence

To complete the Cancer registration statistics for England publication, NCRAS takes a snapshot of the cancer data from the Cancer Analysis System when the expected registrations for a year are complete. This provides a single, consistent source of cancer registrations. This snapshot allows NCRAS to publish consistent statistics on the:

• counts of registrations of cancer by cancer type (3 and 4 digit ICD10 codes), age, sex and deprivation (from 2019 registrations)
• age-specific rates of cancer incidence by cancer type (3 and 4 digit ICD10 codes) and sex
• age-standardised and non-standardised rates of cancer incidence by cancer type (3 and 4 digit ICD10 codes), sex and deprivation (from 2019 registrations)

From May 2020, the percentage of cancer registrations by stage at diagnosis for all stageable common cancers which have at least 70% completeness are also reported in the Cancer registration statistics publication. The data reported cases from 2013 onwards.

TNM is the staging system used for most cancer sites and has 4 stages. The FIGO system is used to stage gynaecological cancers; the Ann Arbor system is used to stage Hodgkin Lymphomas these both have 4 stages. The International Staging System (ISS) is used to stage myelomas and has 3 stages. NCRAS uses the TNM to complement the staging information provided by the other systems, except for cervix where only FIGO is used. This is because the previous version of FIGO for cervix did not include nodal status (N component of TNM). The new version of FIGO for cervix does now include nodal status, but is slightly different to current TNM staging.

Stage at diagnosis of cancer is an important factor that can affect treatment options and cancer outcomes, such as survival. Earlier diagnosis, that is, usually when cancers are diagnosed at stages 1 and 2 as opposed to stages 3 and 4, is associated with better prognosis on average. It should be noted that not all cancers have a staging system, for example, most brain cancers do not currently have a staging system. The government aims to have 75% of the top 10 cancers diagnosed at stages 1 and 2 by 2028.

The rates presented in the Cancer registration statistics publication are known as cancer incidence rates or cancer mortality rates. A cancer incidence rate is the number of new cancer registrations made in a year within a population. A cancer mortality rates is the number of deaths caused by a cancer in a year within a population. Age-specific rates are rates by age-group. Incidence and mortality rates are usually given per 100,000 population.

Incidence rate = (number of cancer registrations/population) x 100,000

Age-standardised rates are a weighted average of the age-specific cancer rates. All age-standardised cancer rates published since June 2014 have used the 2013 European Standard Population (ESP). The ESP is a set of weights for a population structure, based on an average European age-profile of a population. The weights are applied to age-specific rates to produce age-standardised rates.

Age-standardised incidence rates allow users to make fair comparisons of cancer diagnoses:

• across different regions in England
• with other countries in Europe
• between different time periods

Note: the ESP has an upper age band of 95 and older. England population estimates produced by Office of National Statistics (ONS) currently have an upper age band of 90 and older. This means NCRAS must combine the weights for the 90 to 94 and 95 and older age bands. The upper age band for incidence or mortality calculations is also 90 and older.

The ESP population structure and weights were last updated by Eurostat in 2013. The report The impact of calculating cancer incidence rates using the 2013 European Standard Population describes the impact of changing the ESP from the 1976 ESP to the 2013 ESP.

Age-standardised rates calculated using the 2013 ESP are not comparable to rates calculated with the 1976 ESP. As a part of the change to the 2013 ESP, ONS published a back series of age-standardised cancer incidence rates. These rates cover England from 1971 to 2012 using the 2013 ESP to help users compare rates across time. NCRAS will continue to report cancer registration statistics using the 2013 ESP to enable comparisons across time periods.

Cancer Mortality

ONS provides NCRAS with extracts from the annual mortality registration files. ONS document their dataset in the mortality data quality and methodology report. NCRAS uses the dataset to publish the statistics for:

• number of deaths from cancer by cancer type, age, sex and deprivation (from 2019 registrations)
• age-specific rates of cancer mortality by cancer type and sex
• age-standardised and non-standardised rates of cancer mortality by cancer type, sex and deprivation (from 2019 registrations).

When reporting cancer mortality, ‘cancer’ is used to refer to all malignant neoplasms which include 3-digit ICD-10 code C00 to C97, excluding non-melanoma skin cancer (NMSC) (ICD-10 C44). All rates are expressed per 100,000 population and age-standardised rates are standardised to the 2013 ESP.

Statistical accuracy

Rates calculated on low numbers can be hard to interpret. To help users make reliable interpretations, the data reference tables for the publication include:

• age-specific rates where the count for a combination of age, sex and cancer site is 3 or more
• directly age-standardised rates where the total count for a combination of age and cancer site is 10 or more

To help users make reliable interpretations, the publication tables do not include:

• age-specific rates where the count for a combination of age, sex and cancer site is fewer than 2 or less
• directly age-standardised rates where the total count for a combination of age and cancer site is 9 or less.

The publication tables suppress rates with ‘u’ if they are not included for the reasons stated above. Additionally, the publication tables will flag any non-standardised or directly age-standardised rates based on a total count of between 10 and 19 with a ‘u’. This is a warning to users that the small number of diagnoses may affect the reliability of these rates.