Data showing an increasing gap between the incidence of thyroid cancer and deaths from the disease suggest that low-risk cancers are being overdiagnosed and overtreated—and that the use of high-tech imaging technologies including ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), may be to blame. That was the conclusion of an analysis in British Medical Journal (2013;347:f4706).
“High tech imaging technologies such as ultrasound, CT, and MRI can detect very small thyroid nodules, many of which are slow-growing papillary thyroid cancers,” the study's lead author, Juan Pablo Brito, MBBS, an endocrine fellow and health care delivery scholar at Mayo Clinic, said in a news release. As the study notes, however, research has shown that malignant cells are detected in only 10 percent of patients who present with thyroid nodules.
The study authors reviewed epidemiological and observational evidence, and reported these findings:
- Thyroid cancer incidence has increased: The age-standardized incidence of thyroid cancer in women rose from 1.5 cases per 100,000-individual population in 1953 to 7.5 cases per 100,000 in 2002, according to the Cancer Incidence in Five Continents report (with similar relative increases in men).
- Increased thyroid cancer diagnosis has resulted from greater use of imaging technology for other indications: Research has shown that in the U.S., CT use has more than tripled between 1995 and 2005, MRI use more than doubled, and more patients receive a diagnosis of thyroid cancer after an evaluation of an incidentally found thyroid nodule than after evaluation of a symptomatic or palpable nodule.
- Detection of small papillary thyroid cancers in patients without a family history of thyroid cancer or exposure to radiation usually triggers intensive treatment, even though these cancers are unlikely to cause morbidity or premature mortality: Analysis of the U.S. National Cancer Institute's Surveillance Epidemiology and End Results database of 32 years of data showed no significant difference in the death rate from thyroid cancer in patients who did not receive immediate surgery for low-risk papillary thyroid cancers compared with those who did.
- In the past 30 years, surgical removal procedures in the U.S. have tripled, and the number of thyroidectomies for thyroid cancer in the U.S. rose by 60 percent between 1996 and 2006.
The study's authors also note that the unnecessary treatment is costly and can cause harm and long-term quality-of-life concerns. The authors suggest renaming low-risk lesions (those smaller than 20 millimeters) in patients with no family history or radiation exposure and no ultrasound evidence of extraglandular invasion as “micropapillary lesions of indolent course” (microPLICs), noting that a change in nomenclature could reframe the care of these patients and avoid their overtreatment.
And, the study also notes that the epidemiological and observational evidence used could be affected by confounding and selection and reporting biases—and that large randomized trials are required to compare immediate thyroidectomy with surveillance.