This is a multicenter, controlled, randomized phase III study to compare participation rate with two screening rounds of fecal occult blood test (FIT) versus one-time screening colonoscopy in first degree relatives (FDR) of patients diagnosed of colorectal cancer (CRC).

The hypothesis of the study is that annual FIT uptake and colonoscopy when a positive test is higher than that of straightforward colonoscopy. Assuming an uptake of 0.50 for colonoscopy and 0.60 for FIT, a Type I error (alpha) of 5% and a power of 90%, 538 FDRs will be necessary to include in each group.

This is a multicenter, controlled, randomized phase III study to compare participation rate with two screening rounds of FIT versus one-time screening colonoscopy in FDR of patients diagnosed of CRC.

The recruitment process will be programmed through the index case, that will be interviewed to obtain their CRC family history. FDR will be contacted in order to make an appointment in the High-risk CRC Clinic of the participant centers. Randomization will be performed before signing the informed consent to avoid selection bias. A researcher will be responsible to provide detailed information about the study and getting the informed consent. In case of willingness to participate in the study, the FDR will be randomized to one of the following arms: A) One-time colonoscopy; B) annual FIT for two screening rounds and a colonoscopy in case of a positive FIT (cut-off = 10 μg Hemoglobin/g feces). Screening uptake will be defined as the percentage of FDR who participate at least in one of the two FIT screening round in the FIT group or who undergo colonoscopy in the other group. Screening uptake will be calculated under the assumption of intention to screen analysis.

The hypothesis of the study is that annual FIT uptake and colonoscopy when a positive test is higher than that of straightforward colonoscopy. Assuming an uptake of 0.50 for colonoscopy and 0.60 for FIT, a Type I error (alpha) of 5% and a power of 90%, 538 FDRs will be necessary to include in each group.

Inclusion Criteria:

1. FDR with a case index meeting the following conditions: at least one case index < 60 years at diagnosis of the CCR;
2. having ≥ 2 FDRs with CRC regardless the age of the case index at diagnosis;
3. having a sibling with CRC;
4. age <75 years.

Exclusion Criteria:

1. past CRC screening;
2. inflammatory bowel disease or past history of colorectal neoplasia;
3. Family history of hereditary CRC;
4. Abdominal symptoms;
5. Colectomy;
6. Severe comorbidity leading to a poor prognosis (life expectancy < 5 years);
7. Refusal to participate in the study.

Participants were randomized to either colonoscopy or faecal occult blood test