Disease severity and radioactive iodine use for thyroid cancer

Although variation in radioactive iodine (RAI) use for thyroid cancer has been demonstrated, the role of region and nonclinical correlates of use within risk groups has not been investigated.

The objective of the study was to determine the correlates of RAI use within risk groups.

Use of RAI was evaluated across 9 US regions in 85 948 patients with well-differentiated thyroid cancer diagnosed between 2004 and 2008 at 986 hospitals associated with the US National Cancer Database. Cancers were then categorized as low risk (tumor size ≤ 1 cm and American Joint Committee on Cancer stage I disease), medium risk (neither low nor high-risk), and high risk (American Joint Committee on Cancer stage III or IV). Within each risk stratum, the role of region and nonclinical correlates of RAI use were evaluated using hierarchical logistic regression.

Use of RAI was measured.

Rates of RAI use varied across geographic regions from 49% to 66%. Regional differences persisted after controlling for patient and hospital characteristics and evaluating less vs more intensive regions within low-risk [odds ratio (OR) 0.36 (95% confidence interval [CI] 0.25-0.53)], medium-risk [OR 0.23 (95% CI 0.16-0.34)], and high-risk cancers [OR 0.30 (95% CI 0.19-0.49)]. Patterns of RAI use were similar in medium- and high-risk patients. The most nonclinical correlates of use were in low-risk patients.

Similar treatment patterns for the heterogeneous medium-risk thyroid cancer patients compared with the high-risk patients suggest more intensive management in patients with medium-risk disease. The large number of nonclinical correlates of RAI use, including region, imply controversy over indications for RAI.