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Original article
Risk of thyroid cancer in first-degree relatives of patients with non-medullary thyroid cancer by histology type and age at diagnosis: a joint study from five Nordic countries
  1. Mahdi Fallah1,
  2. Eero Pukkala2,3,
  3. Laufey Tryggvadottir4,5,
  4. Jörgen H Olsen6,
  5. Steinar Tretli7,
  6. Kristina Sundquist8,
  7. Kari Hemminki1,8
  1. 1Division of Molecular Genetic Epidemiology, German Cancer Research Center, Heidelberg, Germany
  2. 2Finnish Cancer Registry, Institute for Statistical and Epidemiological Cancer Research, Helsinki, Finland
  3. 3School of Health Sciences, University of Tampere, Tampere, Finland
  4. 4Icelandic Cancer Registry, Reykjavik, Iceland
  5. 5Faculty of Medicine, University of Iceland, Reykjavik, Iceland
  6. 6Institute of Cancer Epidemiology, Copenhagen, Denmark
  7. 7Norwegian Cancer Registry, Oslo, Norway
  8. 8Center for Primary Health Care Research, Lund University, Malmö, Sweden
  1. Correspondence to Dr Mahdi Fallah, Division of Molecular Genetic Epidemiology, German Cancer Research Center, Im Neuenheimer Feld 580, Heidelberg 69120, Germany; m.fallah{at}dkfz.de

Abstract

Background We aimed to estimate lifetime cumulative risk of thyroid cancer (CRTC) in first-degree relatives of patients with non-medullary thyroid cancers (NMTC), including papillary (PTC)/follicular/oxyphilic/anaplastic thyroid carcinoma, by histology and age at diagnosis in patients and their relatives.

Design A population-based cohort of 63 495 first-degree relatives of 11 206 NMTC patients diagnosed in 1955–2009 in Nordic countries was followed for cancer incidence. Standardised incidence ratios (SIRs) were calculated using histology-specific, age-specific, sex-specific, period-specific and country-specific incidence rates as reference.

Results The 0–84-year CRTC in female relatives of a patient with PTC was 2%, representing a threefold increase over the general population risk (SIR=2.9, 95% CI 2.4 to 3.4; Men: CRTC=1%, SIR=2.5, 95% CI 1.9 to 3.3). When there were ≥2 PTC patients diagnosed at age <60 years in a family, CRTC for female relatives was 10% (male 24%). Twins had a 23-fold increased risk of concordant PTC. Family history of follicular/oxyphilic/anaplastic carcinoma increased CRTC in relatives to about 1–2%. Although no familial case of concordant oxyphilic/anaplastic carcinoma was found, familial risks of discordant histology types of NMTC were interchangeably high for most of the types, for example, higher risk of PTC when a first-degree relative had follicular (SIR=3.0, 95%CI 1.7 to 4.9) or anaplastic (SIR=3.6, 95% CI 1.2 to 8.4) carcinoma. The earlier a patient was diagnosed with PTC in a family, the higher was the SIR in his/her younger relatives. There was a tendency towards concordant age at diagnosis of thyroid cancer among relatives of PTC patients.

Conclusions This study provides clinically relevant risk estimates for family members of NMTC patients.

  • Thyroid cancer
  • Familial risk
  • non-medullary thyroid carcinoma
  • Nordic countries
  • cumulative risk

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