Patient Selection

Patients, aged 20 through 90 years, were selected if they were registered with International Classification of Primary Care version 1 (ICPC-1) code D75 (for malignant neoplasm colon/rectum) in the JGPN database from 2007 through 2011, and were registered with the same diagnosis in the Netherlands Cancer Registry, validating diagnoses.

Only patients who initially visited the GP with complaints or symptoms directly or indirectly related to CRC, and were referred by the GP, were included. Patients with substantially missing information or unclear electronic health records contents were excluded.