Increasing Incidence of Thyroid Cancer in the United States, 1973-2002

This study examined the 2.4-fold increase (from 3.6 to 8.7 per 100,000) in thyroid cancer in the United States between 1973 and 2002. Mortality from thyroid cancer remained stable at approximately 0.5 per 100,000. Eighty seven percent of the increase was due to a single type: small papillary thyroid nodules. The study was retrospective, and data were obtained from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Program; statistical analysis was performed using STATA version 9.0. The authors propose—on the basis of this study and autopsy studies that found up to 36 percent of adults harbor incidental thyroid cancers—that the observed increase in thyroid cancer is most likely explained by improved diagnostics and imaging techniques, rather than by a true increase in cancer rates.

Key findings:

  • Widespread use of ultrasonography and fine needle aspiration has led to increased detection of a subclinical (asymptomatic) reservoir of patients with papillary thyroid cancers.
  • “Overdiagnosis” of thyroid cancers is of concern because complete thyroidectomy is usually performed, even for small nodules.
  • Complete thyroidectomy requires lifelong hormone supplementation and carries a small but significant risk of complications such as damage to the recurrent laryngeal nerve and permanent hypoparathyroidism.

Further studies are necessary to decide whether some thyroid cancers can simply be followed rather than treated.