title: Prevalence and prognosis of synchronous colorectal cancer: a Dutch population-based study.
abstract: BACKGROUND
  A noticeable proportion of colorectal cancer (CRC) patients are diagnosed with synchronous CRC. Large population-based studies on the incidence, risk factors and prognosis of synchronous CRC are, however, scarce, and are needed for better determination of risks of synchronous CRC in patients diagnosed with colonic neoplasia.
  
  
  METHODS
  All newly diagnosed CRC between 1995 and 2006 were obtained from the Rotterdam Cancer Registry in The Netherlands, and studied for synchronous CRC.
  
  
  RESULTS
  Of the 13,683 patients diagnosed with CRC, 534 patients (3.9%) were diagnosed with synchronous CRC. The risk of having synchronous CRC was significantly higher in men (OR 1.54, 95% CI 1.29-1.84) and in patients aged >70 years (OR 1.83, 95% CI 1.39-2.40). Synchronous CRC patients had a significantly higher risk of distant metastases (OR 1.69, 95% CI 1.27-2.26). In 34% (184/534) the two tumours were located in different surgical segments. Five-year relative survival of synchronous CRC was similar to patients with solitary CRC after multivariate adjustment for the presence of distant metastases.
  
  
  CONCLUSIONS
  One out of 25 patients diagnosed with CRC presents with synchronous CRC. In the multivariate analysis, survival of patients with synchronous CRC was similar to patients with solitary CRC, when corrected for the presence of distant metastases at first presentation. One third of the synchronous CRC were located in different surgical segments, which stresses the importance of performing total colon examination preferably prior to surgery.
authors.affiliation: Department of Gastroenterology and Hepatology, Erasmus University Medical Centre, 's-Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands. S.mulder.1@erasmusmc.nl
authors.forename: Sanna A
authors.initials: SA
authors.lastname: Mulder
authors.forename: Ries
authors.initials: R
authors.lastname: Kranse
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Damhuis
authors.forename: Johannes H W
authors.initials: JH
authors.lastname: de Wilt
authors.forename: Rob J Th
authors.initials: RJ
authors.lastname: Ouwendijk
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Kuipers
authors.forename: Monique E
authors.initials: ME
authors.lastname: van Leerdam
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D009378:Neoplasms, Multiple Primary / Q000453:epidemiology* / Q000401:mortality*; D009426:Netherlands / Q000453:epidemiology; D015995:Prevalence; D011379:Prognosis; D012307:Risk Factors; D015996:Survival Rate; D055815:Young Adult