Study population
comorbidity, hereditary CRC, CRC, inflammatory bowel disease or, colorectal neoplasia
This randomized controlled trial was carried out in 7 Spanish regions (Aragón, Basque Country, Canary Islands, Cataluña, Galicia, Madrid, and Valencia), including 12 tertiary hospitals, between February 25, 2016 and December 31, 2021. Asymptomatic screening-naïve FDR (parents, siblings, and children) of index cases diagnosed with CRC during the previous 24 months were eligible if they met the following inclusion criteria: (a) having 1 index case younger than 60 years at the time of CRC diagnosis, having 2 or more index cases or a sibling with CRC, regardless of age at diagnosis; (b) age over 40 years or 10 years less than that of the youngest index case in the immediate family; (c) histological confirmation of CRC diagnosis of the index case; and (d) signing an informed consent form. Exclusion criteria included (a) previous CRC screening; (b) personal history of inflammatory bowel disease or colorectal neoplasia; (c) family history of hereditary CRC; (d) abdominal symptoms that required investigation; (e) previous colectomy; and (f) severe comorbidity that entailed a poor prognosis (average life expectancy less than 5 years). The trial was registered at 