title: Thyroid cancer incidence patterns in Sao Paulo, Brazil, and the U.S. SEER program, 1997-2008.
abstract: BACKGROUND
  Thyroid cancer incidence has risen steadily over the last few decades in most of the developed world, but information on incidence trends in developing countries is limited. Sao Paulo, Brazil, has one of the highest rates of thyroid cancer worldwide, higher than in the United States. We examined thyroid cancer incidence patterns using data from the Sao Paulo Cancer Registry (SPCR) in Brazil and the National Cancer Institute's Surveillance Epidemiology End Results (SEER) program in the United States.
  
  
  METHODS
  Data on thyroid cancer cases diagnosed during 1997-2008 were obtained from SPCR (n=15,892) and SEER (n=42,717). Age-adjusted and age-specific rates were calculated by sex and histology and temporal patterns were compared between the two populations.
  
  
  RESULTS
  Overall incidence rates increased over time in both populations and were higher in Sao Paulo than in the United States among females (SPCR/SEER incidence rate ratio [IRR]=1.65) and males (IRR=1.23). Papillary was the most common histology in both populations, followed by follicular and medullary carcinomas. Incidence rates by histology were consistently higher in Sao Paulo than in the United States, with the greatest differences for follicular (IRR=2.44) and medullary (IRR=3.29) carcinomas among females. The overall female/male IRR was higher in Sao Paulo (IRR=4.17) than in SEER (IRR=3.10) and did not change over time. Papillary rates rose over time more rapidly in Sao Paulo (annual percentage change=10.3% among females and 9.6% among males) than in the United States (6.9% and 5.7%, respectively). Regardless of sex, rates rose faster among younger people (<50 years) in Sao Paulo, but among older people (≥50 years) in the United States. The papillary to follicular carcinoma ratio rose from <3 to >8 among both Sao Paulo males and females, in contrast to increases from 9 to 12 and from 6 to 7 among U.S.males and females, respectively.
  
  
  CONCLUSIONS
  Increased diagnostic activity may be contributing to the notable rise in incidence, mainly for papillary type, in both populations, but it is not likely to be the only reason. Differences in iodine nutrition status between Sao Paulo and the U.S. SEER population might have affected the observed incidence patterns.
authors: Institute of Radiation Protection and Dosimetry, Brazilian Nuclear Energy Commission, Rio de Janeiro, Brazil. lene@ird.gov.br
authors: Lene H S
authors: LH
authors: Veiga
authors: Gila
authors: G
authors: Neta
authors: Briseis
authors: B
authors: Aschebrook-Kilfoy
authors: Elaine
authors: E
authors: Ron
authors: Susan S
authors: SS
authors: Devesa
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology; D000367:Age Factors; D001938:Brazil / Q000453:epidemiology; D002277:Carcinoma / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology; D018278:Carcinoma, Neuroendocrine; D002291:Carcinoma, Papillary; D019049:Developed Countries; D003906:Developing Countries; D004032:Diet / Q000009:adverse effects / Q000208:ethnology; D005260:Female; D019456:Health Transition; D006801:Humans; D015994:Incidence; D007455:Iodine / Q000008:administration & dosage / Q000172:deficiency; D008297:Male; D009752:Nutritional Status; D012042:Registries; D018426:SEER Program; D012737:Sex Factors; D062211:Spatio-Temporal Analysis; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000453:epidemiology* / Q000208:ethnology / Q000209:etiology; D014481:United States / Q000453:epidemiology
chemical_list: D007455:Iodine