Increased imaging improved early detection in well-differentiated thyroid cancer

Issue: November 25, 2014

CORONADO, Calif. — Patients diagnosed with well-differentiated thyroid cancer after 2000 were more likely to exhibit lower risk disease, according to study results presented at the American Thyroid Association Annual Meeting.

Researchers noted that the use of post-diagnosis imaging has increased among all patients, regardless of the level of disease, with the largest growth observed in the use of PET scans.

“This study contributes to the discussion regarding post-diagnosis imaging because there is very limited data on use of surveillance imaging in thyroid cancer,” Jaime L. Wiebel, MD, from the division of metabolism, endocrinology and diabetes at the University of Michigan, told HemOnc Today. “We are doing more imaging today compared to 20 years ago. We saw a particularly large growth in the use of PET scan, [which] was unexpected because we are diagnosing more low-risk disease.”

Jaime L. Wiebel

To assess post-diagnosis imaging patterns and establish patient characteristics linked to likelihood of imaging, Wiebel and colleagues reviewed the SEER-Medicare linked database from 1991 to 2009 to identify 23,669 patients diagnosed with localized, regional or distant well-differentiated thyroid cancer.

The researchers reviewed medical claims data and evaluated use of thyroid ultrasound, radioactive iodine (I-131) scan or PET scan within 3 years after patient diagnosis. Wiebel and colleagues assessed imaging utilization trends for the study period through a linear regression analysis, then used multivariable logistic regression to estimate the probability of imaging centered on patient characteristics.

According to study results, patients diagnosed after 2001 were more likely to exhibit localized disease (P<.001) and tumors <1 cm (P<.001).

Wiebel and colleagues observed an increased use of thyroid ultrasound (P≤.001) and I-131 scans (P=.003) among patients with localized disease, with similar increases noted in scans performed on patients with regional disease. The researchers also observed an increase in the number of thyroid ultrasound (P=.001) and I-131 scans (P=.015) performed among patients with distant disease.

After controlling for patient characteristics, the researchers found that patients diagnosed from 2001 to 2009 were at increased probability to receive thyroid ultrasound than patients diagnosed from 1991 to 2000 (OR=2.15; 95% CI, 2.02-2.28).

In addition, patients diagnosed after 2000 were more likely to receive an I-131 scan (OR=1.44; 95% CI, 1.35-1.54). PET scan use from 2005 to 2009 vs. 1996 to 2004 increased 32.4-fold (P≤.001) among patients with localized disease, 13.1-fold (P<.001) among those with regional disease and 33.4-fold (P<.001) in patients with distant well-differentiated thyroid cancer.

“We report a very large increase in the use of PET scan that we think warrants further investigation into indications for imaging, as well as any effect on patient outcomes,” Wiebel said. “Hopefully, with further investigation, we can determine which patients benefit from advanced imaging tests and when they can be avoided.”

For more information:

Wiebel JL. Poster #65. Presented at: American Thyroid Association Annual Meeting; Oct. 29-Nov. 2, 2014; Coronado, Calif.

Disclosure: The researchers reported no relevant financial disclosures.