A population‐based linked cohort of cancer and primary care data: A new source to study the management of cancer in primary care

OBJECTIVE: Insight into the management of cancer in the primary care setting is pivotal to improve early recognition and survival of cancer patients. Therefore, the Netherlands Cancer Registry (NCR) was linked to the General Practitioner (GP) Database of the PHARMO Database Network to make this research possible. METHODS: The NCR collects tumour data on all newly diagnosed cancer patients, whereas the GP Database comprises data from electronic patient records registered by GPs. Databases were linked using a probabilistic record linkage technology. RESULTS: Through record linkage of the NCR and the GP Database, we have established a large population‐based cohort (NCR‐PHARMO GP cohort) of 135,868 cancer patients. Data are available on demographics, tumour characteristics, primary health care use before and after cancer diagnosis including medication use, medical conditions, laboratory tests, and referrals. Data can be used for a number of different studies, for example, to study the diagnostic pathway in the primary care setting in order to identify possibilities for early recognition. CONCLUSION: The NCR‐PHARMO GP cohort provides rich data on the primary care management of cancer facilitating large‐scale observational cancer research in the primary care setting. The patient‐level linkage allows for long‐term follow‐up of cancer patients, with ongoing annual updates.