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Increased thyroid cancer prevalence likely due to overdetection
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Although incidental differentiated thyroid cancer is common, the increased prevalence in recent decades likely is a result of increased detection rather than increased tumorigenesis, a meta-analysis showed.
“Given that the increasing incidence is mainly of subcentimeter tumors, a truly increasing incidence should be reflected by an expanding incidental thyroid cancer reservoir,” Luis Furuya-Kanamori, MBBS, MEpi, MPH, of the Research School of Population Health at Australian National University, Canberra, and colleagues wrote. “The status of this reservoir can be examined using data from case series of autopsies performed on patients who were not known to have thyroid disease at the time of death. … Therefore, we undertook to combine all published autopsy series to estimate the time trend in pooled prevalence and to evaluate possible factors related to the differences in prevalence across studies.”
Furuya-Kanamori and colleagues evaluated data from 35 autopsy studies — found in the PubMed, Embase and Web of Science databases — that included patients who had no known history of thyroid pathology and reported the prevalence of incidental differentiated thyroid cancer (n = 12,834). All studies were conducted from 1949 to 2007.
The researchers reported an incidental differentiated thyroid cancer prevalence of 4.1% (95% CI, 3-5.4) in the partial examination subgroup, and 11.2% (95% CI, 6.7-16.1) in the whole examination group. When researchers accounted for the intensiveness of thyroid examinations using a regression model, the cancer prevalence stabilized from 1970 onward.
“This study affirms the presence of a substantial reservoir of incidental thyroid cancer that, importantly, has not increased over the past several decades,” Furuya-Kanamori and colleagues wrote.
The researchers also noted thyroid cancer deaths have remained stable over the past 30 years, and that although at least one-third of adults develop small papillary thyroid cancers, most of those cancers never produce symptoms.
“Therefore, it is likely that the increasing incidence of differentiated thyroid cancer is related to increasing detection of stable incidental disease,” Furuya-Kanamori and colleagues wrote. “Strategies to reverse such overdetection and the consequent overtreatment will require methods to both decrease inappropriate imaging and better manage small nodules when detected.” – by Andy Polhamus
Disclosure: The researchers report no relevant financial disclosures.
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