title: Colorectal cancer screening: the time to act is now.
abstract: BACKGROUND
  Colorectal cancer (CRC) is the third most common cancer and the fourth most common cause of cancer deaths globally. However, there is overwhelming evidence that a large proportion of CRC cases and deaths could be prevented by screening. Nevertheless, CRC screening programmes are offered in a minority of countries only and often suffer from low adherence.
  
  
  CONCLUSIONS
  Factors potentially accounting for hesitant implementation of and low adherence to CRC screening may include a lower attention in the public and the media than for other cancers and the fairly long follow-up time needed to fully disclose screening effects on CRC incidence and mortality. The latter results from the very slow development of most CRCs through the adenoma-carcinoma sequence, and it challenges the predominant or even exclusive reliance on evidence from randomized controlled trials in policy decisions on screening offers. Additional key elements of future research should include (1) studies evaluating diagnostic performance of novel biomarkers for non-invasive or minimally invasive CRC screening in true screening settings, (2) modelling studies evaluating expected short- and long-term impact, effectiveness, and cost-effectiveness of various screening options, and (3) timely and close monitoring of process quality and outcomes of existing and planned CRC screening programmes. Most importantly, however, translation of the vast existing evidence on CRC screening into actual screening programmes with the best possible levels of adherence needs to be fostered. This can be best achieved in the context of organized programmes. Depending on available infrastructure and resources, epidemiological patterns, population preferences, and costs, different screening offers might be preferred. According to current evidence, colonoscopy, flexible sigmoidoscopy, and faecal occult blood tests (preferably faecal immunochemical tests) are prime candidates for effective and cost-effective screening options, and microsimulation models should help to tailor their implementation.
  
  
  CONCLUSIONS
  The strong evidence for the large potential of CRC screening in reducing the burden of CRC calls for timely implementation of organized screening programmes where they are not in place yet, and for continuous improvement of existing ones. This should be considered an obligation that is not to be postponed: the time to act is now.
authors.affiliation: Division of Clinical Epidemiology and Aging Research, German Cancer Research Center (DKFZ), INF 581, 69120, Heidelberg, Germany. h.brenner@dkfz.de.|Division of Preventive Oncology, German Cancer Research Center (DKFZ) and National Center for Tumor Diseases (NCT), INF 460, 69120, Heidelberg, Germany. h.brenner@dkfz.de.|German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), INF 280, 69120, Heidelberg, Germany. h.brenner@dkfz.de.
authors.forename: Hermann
authors.initials: H
authors.lastname: Brenner
authors.affiliation: Institute of Medical Biometry and Informatics, University of Heidelberg, INF 305, 69120, Heidelberg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Stock
authors.affiliation: Division of Clinical Epidemiology and Aging Research, German Cancer Research Center (DKFZ), INF 581, 69120, Heidelberg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hoffmeister
mesh_terms: D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000401:mortality; D055088:Early Detection of Cancer; D006801:Humans; D015994:Incidence; D008403:Mass Screening