title: Young patients with colorectal cancer have increased risk of second primary cancers.
abstract: OBJECTIVE
  Because the number of long-term survivors of colorectal cancer has increased, second primary cancer has become an important issue. However, previous studies were heterogeneous in design, and few data for Asia-Pacific area were available.
  
  
  METHODS
  This was a retrospective population-based study conducted using the national database of the Taiwan Cancer Registry. Patients who have histology-proven primary colon cancer and rectal cancer from 1995 to 2005 were enrolled in this study. All second primary cancer events had to be histology proven. The standardized incidence ratio of second primary cancer was used as an indicator. Standardized incidence ratio was counted as the number of observed second primary cancer divided by the expected number of cancer cases in the general population.
  
  
  RESULTS
  A total of 65 648 eligible index patients were enrolled, and 3810 second primary cancer events were identified. The standardized incidence ratio for all of the patients was 1.03 (95% confidence interval: 0.99-1.06), which implied that the risk of second primary cancer was not significantly elevated in the index patients compared with that of the general population. The standardized incidence ratio for the patients aged <50, 50-70 and >70 years was 2.52 (95% confidence interval: 2.28-2.78), 1.18 (95% confidence interval: 1.12-1.23) and 0.80 (95% confidence interval: 0.76-0.84), respectively. In young patients (aged <50 years), the standardized incidence ratio increase was statistically significant and persisted for over 10 years and this significantly increased across all subgroups. The small intestine, the large intestine, the female genital organs and the lungs were the most common sites of second primary cancer in young patients.
  
  
  CONCLUSIONS
  Young patients with colorectal cancer have an increased risk of developing second primary cancer.
authors.affiliation: Department of Oncology, National Taiwan University Hospital, Hsin-Chu Branch, Hsinchu City Department of Oncology, National Taiwan University Hospital, Taipei City Graduate Institute of Oncology, National Taiwan University, Taipei City.
authors.forename: Yi-Hsin
authors.initials: YH
authors.lastname: Liang
authors.affiliation: Department of Oncology, National Taiwan University Hospital, Taipei City Graduate Institute of Oncology, National Taiwan University, Taipei City.
authors.forename: Yu-Yun
authors.initials: YY
authors.lastname: Shao
authors.affiliation: Department of Oncology, National Taiwan University Hospital, Taipei City Center for Comparative Effectiveness Research, National Center of Excellence for Clinical Trial and Research, National Taiwan University Hospital, Taipei City.
authors.forename: Ho-Min
authors.initials: HM
authors.lastname: Chen
authors.affiliation: Center for Comparative Effectiveness Research, National Center of Excellence for Clinical Trial and Research, National Taiwan University Hospital, Taipei City.
authors.forename: Chiu-Lin
authors.initials: CL
authors.lastname: Lai
authors.affiliation: Department of Oncology, National Taiwan University Hospital, Taipei City Department of Internal Medicine, College of Medicine, National Taiwan University, Taipei City.
authors.forename: Zhong-Zhe
authors.initials: ZZ
authors.lastname: Lin
authors.affiliation: Institute of Health Policy and Management, College of Public Health, National Taiwan University, Taipei City.
authors.forename: Raymond Nien-Chen
authors.initials: RN
authors.lastname: Kuo
authors.affiliation: Department of Oncology, National Taiwan University Hospital, Taipei City Graduate Institute of Oncology, National Taiwan University, Taipei City Department of Internal Medicine, College of Medicine, National Taiwan University, Taipei City.
authors.forename: Ann-Lii
authors.initials: AL
authors.lastname: Cheng
authors.affiliation: Department of Oncology, National Taiwan University Hospital, Taipei City Graduate Institute of Oncology, National Taiwan University, Taipei City mslai@cph.ntu.edu.tw khyeh@ntu.edu.tw.
authors.forename: Kun-Huei
authors.initials: KH
authors.lastname: Yeh
authors.affiliation: Center for Comparative Effectiveness Research, National Center of Excellence for Clinical Trial and Research, National Taiwan University Hospital, Taipei City Taiwan Cancer Registry, Taipei City Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei City, Taiwan, ROC mslai@cph.ntu.edu.tw khyeh@ntu.edu.tw.
authors.forename: Mei-Shu
authors.initials: MS
authors.lastname: Lai
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People / Q000706:statistics & numerical data*; D002648:Child; D002675:Child, Preschool; D003110:Colonic Neoplasms / Q000453:epidemiology; D015179:Colorectal Neoplasms / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016609:Neoplasms, Second Primary / Q000453:epidemiology*; D012004:Rectal Neoplasms / Q000453:epidemiology; D012042:Registries; D012189:Retrospective Studies; D012306:Risk; D017741:Survivors / Q000706:statistics & numerical data; D013624:Taiwan / Q000453:epidemiology
keywords: colorectal cancer; second primary cancer; standardized incidence ratio; young patients