title: Asymptomatic colorectal cancer detected by screening.
abstract: OBJECTIVE
  Colorectal cancer screening has become prevalent. To discuss the efficacy of screening, we studied the characteristic of asymptomatic colorectal cancer detected by screening.
  
  
  METHODS
  This is a retrospective review of patients with colorectal cancer treated at our institution. During the past 20 years, 96 of 1,046 cases of colorectal cancer were asymptomatic and detected by screening. Sixty-one of these cases were detected in the recent five years. The initial screening procedures were fecal occult blood test in 51 cases, sigmoidoscopy or colonoscopy in 18, barium enema in 9, and other tests in 18.
  
  
  RESULTS
  Thirteen lesions (14 percent) were smaller than 1.0 cm and 32 (33 percent) were 1-2 cm in size. There were 34 Tis, 21 T1, and 8 T2 tumors. Of the 55 Tis or T1 lesions, 14 showed nonpolypoid growth (5 flat-elevated, 7 flat-elevated with depression, 1 flat, 1 depressed), and 12 of these were detected on endoscopy. Thirty-four cases were TNM Stage 0, 25 were Stage I, 16 were Stage II, 12 were Stage III, and 9 were Stage IV. Sixty-one percent of those detected by screening were in either Stage 0 or Stage I compared with 16 percent in the symptomatic group. Cumulative five-year disease-free survival rates were 100 percent for both Stage 0 and Stage I, 94 percent for Stage II, and 52 percent for Stage III. Overall cumulative five-year survival rate was 87 percent for those detected by screening, compared with 57 percent in symptomatic patients.
  
  
  CONCLUSIONS
  Asymptomatic cancers detected by screening were at a less advanced stage. In particular, many nonpolypoid early cancers were detected by endoscopic screening.
authors.affiliation: Department of Surgery, Tokyo Kosei Nenkin Hospital, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Shida
authors.forename: K
authors.initials: K
authors.lastname: Ban
authors.forename: M
authors.initials: M
authors.lastname: Matsumoto
authors.forename: K
authors.initials: K
authors.lastname: Masuda
authors.forename: T
authors.initials: T
authors.lastname: Imanari
authors.forename: T
authors.initials: T
authors.lastname: Machida
authors.forename: T
authors.initials: T
authors.lastname: Yamamoto
authors.forename: T
authors.initials: T
authors.lastname: Inoue
mesh_terms: D000368:Aged; D001466:Barium Sulfate; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D018572:Disease-Free Survival; D004733:Enema; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D009367:Neoplasm Staging; D009780:Occult Blood; D012189:Retrospective Studies
chemical_list: D001466:Barium Sulfate