Autopsy Data Suggest No Increase in Differentiated Thyroid Cancer Over Past Few Decades

Key Points

  • No increase in the prevalence odds ratios for incidental differentiated thyroid cancer was observed for time periods after 1975 vs 1970–1975.
  • The prevalence odds ratio for before 1970 was lower vs 1970–1975.

The prevalence of incidental differentiated thyroid cancer has remained fairly stable since the 1970s, according to a meta-analysis of autopsy data reported by Furuya-Kanamori et al in the Journal of Clinical Oncology. This finding does not support the reports of manyfold increases in differentiated thyroid cancer over the past few decades.

Study Details

The study involved a literature search for autopsy studies including patients with no known history of thyroid pathology that reported the prevalence of incidental differentiated thyroid cancer. The pooled prevalence of incidental differentiated thyroid cancer was assessed using a fixed-effects meta-analysis with robust error variance. The time effect was analyzed using an inverse-variance weighted logit-linear regression model with robust error variance and a time variable.

Prevalence Over Time

A total of 35 studies conducted between 1949 and 2007 met the inclusion criteria and contributed 42 sets of data on 12,834 autopsies. The prevalence of incidental differentiated thyroid cancer was 4.1% among autopsies with partial examination of the thyroid and 11.2% among those with full examination of the thyroid.

In multivariate analysis adjusting for the intensiveness of examination, compared with the reference group of autopsies performed between 1970 and 1975 (7 data sets), prevalence odds ratio for incidental differentiated thyroid cancer did not differ significantly for time periods of 1976–1980 (4 data sets; 0.91, P = .849), 1981–1985 (11 data sets; 0.90, P = .773), 1986–1990 (5 data sets; 0.68, P = .306), or after 1990 (10 data sets; 0.75, P = .443). However, a significant difference was observed for the period before 1970 (5 data sets; 0.21, P = .001) vs 1970–1975.

The investigators concluded: “The current study confirms that [incidental differentiated thyroid cancer] is common, but the observed increasing incidence is not mirrored by prevalence within autopsy studies and, therefore, is unlikely to reflect a true population-level increase in tumorigenesis. This strongly suggests that the current increasing incidence of [incidental differentiated thyroid cancer] most likely reflects diagnostic detection increasing over time.”

The study was supported by an Endeavour Postgraduate Scholarship, Australian National University Higher Degree Scholarship, Fondo para la Innovacíon, Ciencia y Tecnología Scholarship, and the National Health and Medical Research Council Early Career Fellowship.

Suhail A.R. Doi, PhD, of the Australian National University, Research School of Population Health, is the corresponding author of the Journal of Clinical Oncology article.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.