Invitation letters increase participation in colorectal cancer screening - results from an observational study.

 Participation rates in the German colorectal cancer screening program are low. Starting in 2013, a large health insurance plan in Bavaria, Germany, is sending an additional invitation letter to insured individuals when they turn 50 or 55 years and become eligible for participation in the program. The letter provides detailed information on colorectal cancer screening. We assessed the impact of the invitation letter on utilization rates.  Insurance claims data of a total of 48 343 individuals who had turned 50 or 55 years between 2012 to 2014 were reviewed for utilization rates of screening colonoscopy and fecal blood tests. Utilization rates 1 year prior (2012) and 2 years after introduction of the invitation letter (2013 and 2014) were compared. Furthermore, providers of colorectal cancer screening were determined.  Within 6 months after turning 50 or 55 years, 8.8 - 10.2 % of all insured individuals participated in colorectal cancer screening, with the majority being females. After the introduction of the invitation letter, a moderate increase in participation rates could be observed (increase to 109 % [RR 101.7 - 117.3 %, p = 0.02] in 2014). The uptake rate of screening colonoscopy was significantly higher in recipients of the letter (increase to 138.4 % [RR 110.4 - 173.8 %, p = 0.0043] in 2013 and to 149 % [RR 119.5 - 186.3 %, p = 0.0003] in 2014). Furthermore, a significantly higher proportion of general practitioners and gastroenterologists provided colorectal cancer screening in individuals receiving the invitation letter.  Introduction of an invitation letter can improve participation rates for colorectal cancer screening.