The effect of mailing FIT with the invitation on participation and colonoscopy rates will be evaluated in a randomized controlled trial conducted in the Centre-Val de Loire (CVL) region, involving 64,000 people from the population eligible for colorectal cancer population-based organised screening program (CRC-PBOSP). In the C control group, invitations, test delivery and reminders will be carried out in accordance with the CRC-PBOSP rules at the time of the study. Intervention group B will evaluate two experimental modes of invitation with direct home mailing of the test: * Method B1: invitation with test sent to home without prior information letter * Method B2: information letter followed by invitation with test sent home, designed to optimize participation by first-time subjects (aged 50-51) invited to the CRC-PBOSP for the first time. Ancillary studies will focus 1/ on acceptability of this intervention (qualitative study on a few general practitioners, gastroenterologists and invitees), 2/ on social and geographical inequalities of participation on a subsample of individuals included in EXPEDIT study using ecological indices (EDI, SCALE).