Not much change in incidence rates for other subtypes of thyroid cancer
For other histologic subtypes of thyroid cancer, the trends in incidence rates were relatively stable and low.
However, some countries, such as the United States, China, South Korea, Turkey, and some Northern European countries, saw increases in follicular thyroid cancer, albeit at much lower rates than for papillary thyroid cancer.
Overall, age-standardized rates for follicular thyroid cancer ranged from 0.5 to 2.5 per 100,000 person-years among women and from 0.3 to 1.5 per 100,000 person-years among men. Rates for medullary thyroid cancer were less than one per 100,000 person-years among men and women. For the anaplastic subtype, rates were less than 0.2 per 100,000 person-years.
The team notes that small decreases in anaplastic thyroid cancer rates across the study period were recorded in 21 countries, including Colombia, Lithuania, Bulgaria, Slovenia, Germany, and Norway.
However, Dr. Miranda-Filho said that overall, the incidence rate of anaplastic thyroid cancer “seems to be not affected by the intensity of screening,” whereas the “lack of evidence” on changing trends for follicular disease suggests that opportunistic screening allows only non–life-threatening tumors to emerge “from a large reservoir of subclinical asymptomatic neoplasms in the thyroid glands.”
The study was supported by the French Institut National du Cancer, the Italian Association for Cancer Research, and the Italian Ministry of Health to Centro di Riferimento Oncologico di Aviano. The authors have disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.