title: Metachronous colorectal cancer: necessity of post-operative colonoscopic surveillance.
abstract: OBJECTIVE
  The aim of this study was to identify the occurrence and analyze the characteristics of metachronous colorectal cancers, and to compare the characteristics of these cases (index tumor) with the control group to find any predicting factor that may influence the occurrence of metachronous cancer.
  
  
  METHODS
  The database of colorectal cancer in the Veterans General Hospital-Taipei, from January 1981 to September 2001 was reviewed. In total, 3,846 cases of adenocarcinoma of the colon and rectum, which received curative resection during this period, were found. The criteria of metachronous cancer were: occurrence more than 12 months after curative surgery; with pre-operative complete colonoscopy or one negative post-operative colonoscopic follow-up to rule out synchronous tumor; tumor arising from mucosa at a site other than anastomosis. The age, gender of the patients, the location, pathological characteristics of the metachronous tumors, occurrence of associated adenomas, the number of lesions, and the tumor stage were analyzed and compared with the control group.
  
  
  RESULTS
  In total, 43 cases of metachronous cancer were identified, giving an annual incidence of 0.18%. The distribution of the location of the index tumor of metachronous cases was predominantly left-sided, which was not different from that of the control group. The mean duration of occurrence of metachronous cancer after the primary operation was 71+/-46.6 months. The association of adenomas had no relationship with the occurrence of the metachronous cancer. No significant predicting factors for the development of metachronous tumors were found.
  
  
  CONCLUSIONS
  Lifelong regular post-operative colonoscopic surveillance is essential for colorectal cancer patients.
authors.affiliation: Division of Colon and Rectal Surgery, Department of Surgery, Taipei Veterans General Hospital, National Yang-Ming University, 201 Section 2, Shih-Pai Road, Taipei 112, Taiwan, Republic of China.
authors.forename: Yuan-Tzu
authors.initials: YT
authors.lastname: Lan
authors.forename: Jen-Kou
authors.initials: JK
authors.lastname: Lin
authors.forename: Anna Fen-Yau
authors.initials: AF
authors.lastname: Li
authors.forename: Tzu-Chen
authors.initials: TC
authors.lastname: Lin
authors.forename: Wei-Shone
authors.initials: WS
authors.lastname: Chen
authors.forename: Jeng-Kae
authors.initials: JK
authors.lastname: Jiang
authors.forename: Shung-Haur
authors.initials: SH
authors.lastname: Yang
authors.forename: Huann-Sheng
authors.initials: HS
authors.lastname: Wang
authors.forename: Shih-Ching
authors.initials: SC
authors.lastname: Chang
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology / Q000473:pathology / Q000601:surgery*; D000368:Aged; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000473:pathology / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D016609:Neoplasms, Second Primary / Q000453:epidemiology / Q000473:pathology / Q000601:surgery*; D011184:Postoperative Period; D011446:Prospective Studies; D015996:Survival Rate