title: Blood markers for early detection of colorectal cancer: a systematic review.
abstract: BACKGROUND
  Despite different available methods for colorectal cancer (CRC) screening and their proven benefits, morbidity, and mortality of this malignancy are still high, partly due to low compliance with screening. Minimally invasive tests based on the analysis of blood specimens may overcome this problem. The purpose of this review was to give an overview of published studies on blood markers aimed at the early detection of CRC and to summarize their performance characteristics.
  
  
  METHODS
  The PUBMED database was searched for relevant studies published until June 2006. Only studies with more than 20 cases and more than 20 controls were included. Information on the markers under study, on the underlying study populations, and on performance characteristics was extracted. Special attention was given to performance characteristics by tumor stage.
  
  
  RESULTS
  Overall, 93 studies evaluating 70 different markers were included. Most studies were done on protein markers, but DNA markers and RNA markers were also investigated. Performance characteristics varied widely between different markers, but also between different studies using the same marker. Promising results were reported for some novel assays, e.g., assays based on SELDI-TOF MS or MALDI-TOF MS, for some proteins (e.g., soluble CD26 and bone sialoprotein) and also for some genetic assays (e.g., L6 mRNA), but evidence thus far is restricted to single studies with limited sample size and without further external validation.
  
  
  CONCLUSIONS
  Larger prospective studies using study populations representing a screening population are needed to verify promising results. In addition, future studies should pay increased attention to the potential of detecting precursor lesions.
authors.affiliation: Division of Clinical Epidemiology and Aging Research, German Cancer Research Center (DKFZ), Bergheimer Strasse 20, 69115 Heidelberg, Germany. u.haug@dkfz.de
authors.forename: Sabrina
authors.initials: S
authors.lastname: Hundt
authors.forename: Ulrike
authors.initials: U
authors.lastname: Haug
authors.forename: Hermann
authors.initials: H
authors.lastname: Brenner
mesh_terms: D014408:Biomarkers, Tumor / Q000097:blood* / Q000235:genetics; D005819:Genetic Markers / Q000235:genetics*; D006801:Humans; D009363:Neoplasm Proteins / Q000097:blood / Q000235:genetics; D009367:Neoplasm Staging; D009369:Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D011237:Predictive Value of Tests
chemical_list: D014408:Biomarkers, Tumor; D005819:Genetic Markers; D009363:Neoplasm Proteins