Cancer and population data

Cancer data

Information about the number and type of cancer diagnoses is derived from the Netherlands Cancer Registry (NCR), which is maintained by the Netherlands Comprehensive Cancer Organization (IKNL). The NCR is the only national oncological hospital registry and includes data on all cancer patients in the Netherlands that were diagnosed since 1989. The mission of IKNL is to reduce the impact of cancer. The NCR is an important source of data for research and statistics. A significant portion of the data in the NCR comes from electronic health records (EHRs). In case of a new cancer diagnosis, IKNL receives a notification from a pathology laboratory (via Palga), medical records from hospitals (via DHD) or haematology laboratories. Specially authorized registration employees of IKNL then extract and validate the data. IKNL processes the data for the NCR in compliance with applicable laws and regulations, including the GDPR. More information about privacy and rights and responsibilities can be found in the privacy statement.

Population data

Population data are from Statistics Netherlands (CBS). The population data includes the number of residents per postcode area by gender, 5-year age group, and year, measured on January 1st each year. The analyses are based on the mid-year population, which is the average of the number of residents on January 1st of the respective year and the number of residents on January 1st of the following year.

Choices

The selection of data from the Netherlands Cancer Registry (NCR) is based on the following choices:

• For the Dutch Cancer Atlas, cancer data were aggregated over a period to ensure sufficiently high numbers of cancer diagnoses for the analyses. The time period that was chosen was 2011 to 2022, which is the most recent time period with complete data.
• One of the items recorded in the NCR is the postcode at the time of diagnosis. This postcode was used in the analyses. It was not possible to account for relocations in the analysis.
• The international rules of the International Association of Cancer Registries (IACR) were applied for dealing with multiple cancer diagnoses per person. This means that multiple tumours in the same organ are generally counted only once per person (for example, breast cancer in the left and right breast), but two tumours in different organs are both counted (for example, lung cancer and prostate cancer). The results in the atlas therefore reflect the variation in cancer diagnoses (with a unique primary location) and not necessarily the number of people with cancer.
• Cancer types that are too rare for reliable spatial analyses at the 3-digit postcode level are not included in the atlas. Also, some tumours are grouped together for the analyses to ensure sufficient numbers. It is not possible to separately display the geographical variation of individual tumour types within these groups. The cancer types included in each group are shown in this table.
• The group 'all cancers’ consists of all invasive cancers excluding basal cell carcinoma of the skin and including ductal carcinoma in situ (DCIS) and non-invasive cancers of the bladder and urinary tract.
• The classification of liver cancer and bile duct cancer differs from the common classification. In addition to hepatocellular carcinoma and intrahepatic bile duct cancer, proximal extrahepatic bile duct cancer is included. This was done because both liver and bile duct cancer are rare, making it impossible to reliably study the geographic variation of individual cancer types at the 3-digit postcode level.
• Breast cancer includes both invasive mammary carcinoma and ductal carcinoma in situ (DCIS). Even though DCIS is non-invasive, its treatment is often similar to the treatment of invasive mammary carcinoma. Also, with about 2,000 patients per year, DCIS makes up a significant portion of the number of breast cancer diagnoses. The atlas shows the geographical variation of breast cancer for women only, even though this type of cancer also occurs in men. The number of breast cancer diagnoses in men is very low, which means it was not possible to perform reliable geographic analyses at the 3-digit postcode level for male patients.
• For cancer of the bladder and the urinary tract, both invasive and non-invasive tumours are included in the analyses, because more than half of patients with non-invasive tumours require a significant amount care due to a high risk of disease recurrence.