CRCBaSe: a Swedish register-based resource for colorectal adenocarcinoma research

ObjectivesTo facilitate high-quality register-based research on colorectal cancer (CRC) in Sweden by constructing a database consisting of CRC patients, matched comparators, and relatives.Material and methodsPatients with adenocarcinoma in the colon and/or rectum were identified in the Swedish Colorectal Cancer Register, a nationwide quality-of-care register. For each patient, six comparators from the general population were matched on birth year, sex, year of CRC diagnosis, and county. Comparators were free from CRC at the time of matching, but could later become cases. For both patients and comparators, first-degree relatives (parents, siblings, and children) were identified. Information from nationwide population-based registers was retrieved and linked to each individual in the database using the personal identification number unique to all Swedish residents.ResultsA total of 76,831 CRC patients diagnosed between 1995 and 2016 were identified (51% colon, 49% rectal; before 2007 only rectal cancer patients were included). Among all patients, 37% were stage I-II, 22% stage III, and 22% stage IV. The median follow-up time was 11.9 years (inter-quartile range, IQR: 8.6-15.3). Together with comparators and relatives, the database contains 2,413,139 individuals with information on demographics, dates and causes of death, in- and outpatient healthcare records, cancer diagnoses, prescribed and dispensed drugs, childbirths (among women), and social security information (such as sick leave and early retirement).ConclusionThe Colorectal Cancer Database Sweden (CRCBaSe) is a large and unique register-based data research platform, which opens up for clinically important, large epidemiological studies with innovative design in the field of colorectal adenocarcinoma.