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Low-risk thyroid cancer diagnoses increasing as ultrasound use rises
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The use of thyroid ultrasound as initial imaging for older adults increased by more than 20% per year between 2002 and 2013, corresponding with an increased rate of low-risk thyroid cancer diagnoses during the same period, according to an analysis of Medicare claims data over 12 years.
“This study implies that individuals who live in regions with high use of thyroid ultrasound are more likely to be diagnosed with thyroid cancer, including low-risk thyroid cancer,” Megan R. Haymart, MD, associate professor of medicine, metabolism, endocrinology and diabetes at the University of Michigan, told Endocrine Today. “These findings suggest a need to reduce the harms associated with overdiagnosing thyroid cancer by either reducing thyroid ultrasound use, applying nodule risk stratification more broadly or targeting interventions to reduce unnecessary thyroid ultrasound and fine-needle aspiration in subgroups of patients at low likelihood of benefit, eg, older adults with multiple comorbidities.”
Haymart and colleagues analyzed longitudinal thyroid imaging patterns and sequence of imaging using Medicare claims data from adults aged at least 65 years between 2001 and 2014 (n = 2,407,440), as well as thyroid cancer diagnoses, using Medicare data linked to Surveillance, Epidemiology and End Results (SEER) registry to measure cancer incidence (n = 12,540). Mean age of the patients for the cohort was 76 years, with 58.3% women and 84.2% residing in a metro region.
Researchers used linear mixed-effects modeling to determine factors associated with thyroid cancer incidence over time, and logistic regression analysis using individual-level Medicare data to determine patient characteristics associated with the receipt of thyroid ultrasound as initial imaging compared with patients who received no imaging.
The researchers found that thyroid ultrasound use as initial imaging per 100,000 people enrolled in Medicare increased at a rate of 20.9% per year between 2002 and 2013 (P < .001). When measured at the patient-level and determining the aggregated mean per year for all 12 years, the researchers observed that most patients with differentiated thyroid cancer had papillary thyroid cancer (85.7%) and localized disease (69.9%), with more than one-third of the cohort having a tumor size of 1 cm or less (35.6%).
In multivariable analysis, researchers found that use of thyroid ultrasound was associated with thyroid cancer incidence (P < .001), with the relationship persisting in subgroup analyses with papillary thyroid cancer (P < .001), localized papillary thyroid cancer (P = .004) and localized papillary thyroid cancer with tumors 1 cm or less (P = .01).
“We found that, over time, area-level use of thyroid ultrasound as initial imaging has increased and that this rise in the use of ultrasound correlates with more thyroid cancer diagnoses, including more diagnoses of low-risk thyroid cancer,” Haymart said.
Researchers also compared projected thyroid cancer incidence based on actual rates of thyroid ultrasound use between 2002 and 2013 vs. incidence with thyroid ultrasound use set at 2002 levels from 2003 to 2013. In this analysis, there were 1,833 patients who would not have been diagnosed with thyroid cancer if ultrasound use remained stable at 2002 levels, they wrote.
“Since the largest geographic coverage available with SEER-Medicare is approximately 27.8% of the population, we estimate that in the United States, at least 6,594 adults aged 65 years were diagnosed with thyroid cancer from 2003 to 2013 as a result of an increase in the use of thyroid ultrasounds as initial imaging,” the researchers wrote. “Since this estimate only includes patients enrolled in Medicare Part A and B and non-HMO, actual numbers would be even larger.”
In an interview, Haymart said thyroid cancer is a heterogeneous cancer with many patients having an excellent prognosis, including some patients with indolent disease that may never cause harm.
“In contrast, there is a small subset of patients who have aggressive, potentially fatal disease,” Haymart said. “Future research will need to identify those patients at risk for overdiagnosis of low-risk, potentially indolent disease vs. those at risk for aggressive, potentially fatal disease. This will allow for targeted interventions to reduce the overdiagnosis of low-risk thyroid cancer.” – by Regina Schaffer
For more information:
Megan R. Haymart, MD, can be reached at the University of Michigan Health System, North Campus Research Complex, 2800 Plymouth Road, Building 16, Room 408E, Ann Arbor, MI 48109; email: meganhay@med.umich.edu.
Disclosures: The authors report no relevant financial disclosures.
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