Background: Although subjects with first-degree relatives (FDR) with a history of colorectal cancer (CRC) are at increased risk for CRC, compliance to screening colonoscopy is suboptimal. Computed tomographic colonography (CTC) has been recognized as an alternative for CRC screening in average risk subjects, but less information is available on its performance in FDRs.

Aims: To prospectively assess the accuracy of CTC as a screening tool in FDRs using colonoscopy (OC) with segmental unblinding as reference standard.

Methods: Consecutive patients admitted with CRC diagnosis (index case, IC) were prospectively evaluated. Following the systematic identification of ICs with inherited predispositions to CRC, ICs who agreed to contact their FDRs ≥40 years old were included. Available FDRs were invited to undergo non-cathartic CTC, with OC the following day. Sensitivity/specificity/PPV/NPV of CTC was assessed for detecting subjects with any lesion ≥6 mm, ≥10 mm, and for advanced neoplasia ≥6 mm.

Inclusion Criteria:

• Family history for CRC (first degree)
• Age >40 years old

Exclusion Criteria:

• Contraindications to colonoscopy or CT colonography
• Pregnancy