title: Comparative analysis of patients with clinically diagnosed colorectal cancer and those detected by mass screening.
abstract: OBJECTIVE
  To analyze the differences and similarities between patients with colorectal cancer (CRC) who had been clinically diagnosed (CD) and those detected by mass screening (MS), and thus clarify the practical significance of CRC screening in China.
  
  
  METHODS
  All the data for the CRC patients in the CD group were collected by registration through a cohort study, and the patients in the MS group were selected from mass screening of a natural population of 19 852 in Beijing Metropolitan area. CRC was confirmed pathologically in both groups.
  
  
  RESULTS
  Patients over the age of 50 years with CRC comprised 81.9% of the CD group and 83.3% of the MS group; the percentage of Dukes A + B was 41.1% and 91.7%, respectively; 0.28% of individuals with risk factors in the MS group were found to have CRC, whereas 0.05% did not (P < 0.05). Endoscopically, 44.7% of the protruding type CRC were Dukes A or B compared with only 10% of the ulcerated type (chi(2) = 22.304, P < 0.001). The positivity rate of the fecal occult blood (FOB) test was 79.9% in Dukes A + B and 82.0% in Dukes C + D, showing no difference between the FOB test and Dukes staging in diagnosing CRC (chi(2) = 0.087, P = 0.768). The percentage of patients with increased serum concentration of carcinoembryonic antigen in Dukes C + D was significantly higher than that in Dukes A + B (chi(2) = 5.547, P = 0.019). Among the moderately and well-differentiated CRC, 51.8% (159/307) were Dukes A + B, resulting in a significant difference (chi(2) = 14.504, P < 0.001). There was a familial history of malignancies in 17.9% of CRC cases and 14.6% of their first-degree relatives suffered from malignant tumors.
  
  
  CONCLUSIONS
  The incidence of CRC in Beijing Metropolitan area has been rising significantly. The staging and prognosis of CRC involves symptomatology, laboratory tests, endoscopic findings and pathologic characteristics. Mass screening is effective for detecting early CRC in China.
mesh_terms: D000367:Age Factors; D000368:Aged; D002272:Carcinoembryonic Antigen / Q000097:blood; D015331:Cohort Studies; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000150:complications / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D009367:Neoplasm Staging; D010375:Pedigree; D011446:Prospective Studies
chemical_list: D002272:Carcinoembryonic Antigen