title: Protocol of a thyroid cancer longitudinal study (T-CALOS): a prospective, clinical and epidemiological study in Korea.
abstract: BACKGROUND
  Thyroid cancer incidence in Korea is the highest in the world and has recently increased steeply. However, factors contributing to this sudden increase have not been fully elucidated, and few studies have explored the postoperative prognosis. The Thyroid Cancer Longitudinal Study (T-CALOS) was initiated with three aims: (1) to identify factors predicting quality of life, recurrence, and incidence of other diseases after thyroid cancer treatments; (2) to investigate environmental exposure to radiation, toxicants and molecular factors in relation to tumour aggressiveness; and (3) to evaluate gene-environment interactions that increase thyroid cancer in comparison with healthy participants from a pool of nationwide population-based healthy examinees.
  
  
  METHODS
  T-CALOS enrols patients with incident thyroid cancer from three general hospitals, Seoul National University Hospital, Seoul National University Bundang Hospital and National Medical Center, Korea. The study is an ongoing project expecting to investigate 5000 patients with thyroid cancer up until 2017. Healthy examinees with a normal thyroid confirmed by sonography have been enrolled at the Healthy Examination Center at Seoul National University Hospital. We are also performing individual matching using two nationwide databases that are open to the public. Follow-up information is obtained at patients' clinical visits and by linkage to the national database. For statistical analysis, we will use conditional logistic regression models and a Cox proportional hazard regression model. A number of stratifications and sensitivity analyses will be performed to confirm the results.
  
  
  BACKGROUND
  Based on a large sample size, a prospective study design, comprehensive data collection and biobank, T-CALOS has been independently peer-reviewed and approved by the three hospitals and two funding sources (National Research Foundation of Korea and Korean Foundation for Cancer Research). The results of T-CALOS will be published according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) criteria.
authors.affiliation: Department of Surgery, Seoul National University Hospital & College of Medicine, Seoul, Korea Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea Division of Surgery, Thyroid Center, Seoul National University Cancer Hospital, Seoul, Korea.
authors.forename: Kyu Eun
authors.initials: KE
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Young Joo
authors.initials: YJ
authors.lastname: Park
authors.affiliation: Department of Family Medicine, Health Promotion Center for Cancer survivor, Seoul National University Hospital, Seoul, Korea.
authors.forename: Belong
authors.initials: B
authors.lastname: Cho
authors.affiliation: Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea Department of Biomedical Science, Seoul National University Graduate School, Seoul, Korea Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Yunji
authors.initials: Y
authors.lastname: Hwang
authors.affiliation: Department of Surgery, Seoul National University Bundang Hospital, Seongnam-si, Gyeonggi-do, Korea.
authors.forename: June Young
authors.initials: JY
authors.lastname: Choi
authors.affiliation: Department of Surgery, Seoul National University Hospital & College of Medicine, Seoul, Korea Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea Division of Surgery, Thyroid Center, Seoul National University Cancer Hospital, Seoul, Korea.
authors.forename: Su-Jin
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Kangwon National University Hospital, Chuncheon, Gangwon-do, Korea.
authors.forename: Hoonsung
authors.initials: H
authors.lastname: Choi
authors.affiliation: Department of Family Medicine, Health Promotion Center for Cancer survivor, Seoul National University Hospital, Seoul, Korea.
authors.forename: Ho-Chun
authors.initials: HC
authors.lastname: Choi
authors.affiliation: Department of Family Medicine, Health Promotion Center for Cancer survivor, Seoul National University Hospital, Seoul, Korea.
authors.forename: Ah Reum
authors.initials: AR
authors.lastname: An
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Do Joon
authors.initials: DJ
authors.lastname: Park
authors.affiliation: Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea Department of Biomedical Science, Seoul National University Graduate School, Seoul, Korea Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Sue K
authors.initials: SK
authors.lastname: Park
authors.affiliation: Department of Surgery, Seoul National University Hospital & College of Medicine, Seoul, Korea Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea Division of Surgery, Thyroid Center, Seoul National University Cancer Hospital, Seoul, Korea Department of Surgery, National Medical Center, Seoul, Korea.
authors.forename: Yeo-Kyu
authors.initials: YK
authors.lastname: Youn
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004781:Environmental Exposure / Q000009:adverse effects*; D015340:Epidemiologic Research Design; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D011788:Quality of Life; D012008:Recurrence; D056910:Republic of Korea; D013961:Thyroid Gland / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000209:etiology / Q000235:genetics / Q000628:therapy
keywords: EPIDEMIOLOGY