Impact of a Doctor's Invitation on Participation in Colorectal Cancer Screening: A Cluster Randomized Trial

There is a need to improve participation in colorectal cancer screening. Our objective was to assess the impact of a signature from the patient's general practitioner on a letter inviting patients to participate in a colorectal cancer screening.

We conducted a cluster randomized controlled trial with 57 general practitioners established in Paris for more than 5 years, randomized to intervention or usual-care arms. There were 3422 patients included, ages 50-74 years, from general practitioner patient files, and eligible for an invitation letter or a reminder letter to participate in the national population-based screening program. In the intervention arm, patients received a standard letter signed by their general practitioner inviting them to visit the general practitioner's office for a fecal occult blood test if they were eligible. Control patients received the standard invitation letter or the standard reminder. All letters were sent by the district screening organization. The main outcome was the proportion of patients who took the fecal occult blood test within 6 months after the invitation.

Among patients eligible for the study, 508 (14.8%) took a fecal occult blood test after being invited; 285 (15%; 95% confidence interval [CI], 13.5-16.7) in the intervention group and 223 (14.6%; 95% CI, 12.9-16.5) in the control group, with no statistical difference between the 2 groups (odds ratio 1.04; 95% CI, 0.83-1.31; P = .731).

The addition of a general practitioner's signature to a standard letter inviting patients to take a fecal occult blood test had no impact on the frequency of patients taking the fecal occult blood test in the Paris program of colorectal cancer screening.