(HealthDay News) — The increasing incidence of small and indolent thyroid cancer and stable mortality rates suggest overdiagnosis, according to an analysis published online Aug. 27 in BMJ.

Noting that thyroid cancer is the most common endocrine malignancy and one of the fastest growing diagnoses, Juan P. Brito, M.D., from the Mayo Clinic in Rochester, Minn., and colleagues discuss the impact of the introduction of neck ultrasonography into routine endocrinological practice in the 1980s and increased use of computed tomography and magnetic resonance imaging.

The researchers note that the new imaging methods allowed detection and biopsy of nodules as small as 2 mm. Since the early 1980s, the incidence of thyroid cancer increased worldwide, with considerable variation between countries. The incidence in the United States increased from 3.6 cases per 100,000 population in 1973 to 11.6 cases in 2009, with the most indolent form of thyroid cancer (small papillary thyroid cancers) accounting for 90 percent of cases. The gap between thyroid cancer incidence and death rates from papillary thyroid cancer has widened, with death rates stable at 0.5 per 100,000 population in 1979 and 2009. Observational evidence suggests that small papillary thyroid cancers may never progress to cause symptoms or death. Harms of overdiagnosis include increased physical complications, financial and psychosocial burdens, and lifelong thyroid replacement therapy for patients with thyroidectomy.

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“The incongruity between the increased incidence and stable mortality is most likely an effect of overdiagnosis,” the authors write. “This is exposing patients to treatments inconsistent with their prognosis. Both the overdiagnosis and overtreatment of this form of cancer need to be fully recognized.”

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