Effects of Alternative Offers of Screening Sigmoidoscopy and Colonoscopy on Utilization and Yield of Endoscopic Screening for Colorectal Neoplasms: Protocol of the DARIO Randomized Trial

BACKGROUND: Flexible sigmoidoscopy and colonoscopy are recommended screening options for colorectal cancer (CRC). Despite colonoscopy being offered for CRC screening in Germany, the uptake of this offer has been very limited. OBJECTIVE: The objective of this study was to assess the potential for increasing use of endoscopic CRC screening and the detection of advanced colorectal neoplasms by offering the choice between use of flexible sigmoidoscopy and colonoscopy. METHODS: The DARIO study includes a cross-sectional study (part I), followed by a prospective 2-arm randomized controlled intervention trial (part II) with an associated biobank study (part III). Participation is possible in part I of the DARIO study only, parts I and II, or all 3 study parts. After obtaining informed consent from the municipalities, 12,000 people, aged 50-54 years, from the Rhine-Neckar region in Germany were randomly selected from residential lists of the responsible population registries and invited to complete a standardized questionnaire to investigate the nature, frequency, timing, and results of previous CRC screening and eventual diagnostic colonoscopies. In study part II participants from study part I with no colonoscopy in the preceding 5 years are randomized into 2 arms: arm A offering screening colonoscopy only, and arm B offering both options, either screening colonoscopy or screening sigmoidoscopy. The primary endpoint is the proportion of participants in whom colorectal neoplasms >0.5 cm are detected and removed at screening endoscopy. The secondary endpoints are the detection rate of any neoplasm and use of any endoscopic screening. Part III of the study will use samples from participants in study part II to construct a liquid and tissue biobank for the evaluation of less invasive methods of early detection of colon cancer and for the more detailed characterization of the detected neoplasms. Blood, urine, stool, and saliva samples are taken before the endoscopy. Tissue samples are obtained from the neoplasms removed during endoscopy. RESULTS: A total of 10,568 from 12,000 randomly selected women and men aged 50-54 years living in the Rhine-Neckar-Region of Germany have been invited for participation. The remaining 1432 (11.93%) could not be invited because they reached the age of 55 at the time of contact. Of those invited, 2785/10,568 (26.35%) participated in study part I; 53.60% (1493/2785) of these participants were female. Study parts II and III are ongoing. CONCLUSIONS: This study will answer the question if alternative offers of either screening sigmoidoscopy or screening colonoscopy will increase utilization and effectiveness of endoscopic CRC screening compared with an exclusive offer of screening colonoscopy. In addition, alternative noninvasive screening tests will be developed and validated. TRIAL REGISTRATION: German Clinical Trials Register DRKS00018932; https://www.drks.de/drks_web/navigate.do? navigationId=trial.HTML&TRIAL_ID=DRKS00018932 INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/17516