Endocrinol Metab.  2018 Jun;33(2):228-235. 10.3803/EnM.2018.33.2.228.

Star-Shaped Intense Uptake of ¹³¹I on Whole Body Scans Can Reflect Good Therapeutic Effects of Low-Dose Radioactive Iodine Treatment of 1.1 GBq

• Kong SH
• Lim JA
• Song YS
• Moon S
• Kim YA
• Kim MJ
• Cho SW
• Moon JH
• Yi KH
• Park DJ
• Cho BY
• Park YJ

• KMID: 2420491
• DOI: http://doi.org/10.3803/EnM.2018.33.2.228

Abstract

BACKGROUND
After initial radioactive iodine (RAI) treatment in differentiated thyroid cancer patients, we sometimes observe a star-shaped region of intense uptake of 131I on whole body scans (WBSs), called a "˜star artifact.' We evaluated the clinical implications of star artifacts on the success rate of remnant ablation and long-term prognosis.
METHODS
Total 636 patients who received 131I dose of 1.1 GBq for the initial RAI therapy and who did not show distant metastasis at the time of diagnosis were retrospectively evaluated. A negative second WBS was used for evaluating the ablation efficacy of the RAI therapy. Among them, 235 patients (36.9%) showed a star artifact on their first WBS.
RESULTS
In patients with first stimulated thyroglobulin (sTg) levels ≤2 ng/mL, patients with star artifacts had a higher rate of negative second WBS compared with those without star artifacts (77.8% vs. 63.9%, P=0.044), and showed significantly higher recurrence-free survival (P=0.043) during the median 8.0 years (range, 1.0 to 10.0) of follow-up. The 5- and 10-year recurrence rates (5YRR, 10YRR) were also significantly lower in patients with star artifacts compared with those without (0% vs. 4.9%, respectively, P=0.006 for 5YRR; 0% vs. 6.4%, respectively, P=0.005 for 10YRR). However, ablation success rate or recurrence-free survival was not different among patients whose first sTg levels >2 ng/mL regardless of star artifacts.
CONCLUSION
Therefore, star artifacts at initial RAI therapy imply a good ablation efficacy or a favorable long-term prognosis in patients with sTg levels ≤2 ng/mL.

Keyword

Radioactive iodine; Remnant ablation; Star artifact; Thyroid neoplasms; Therapeutic uses

MeSH Terms

Artifacts
Diagnosis
Follow-Up Studies
Humans
Iodine*
Neoplasm Metastasis
Prognosis
Recurrence
Retrospective Studies
Therapeutic Uses*
Thyroglobulin
Thyroid Neoplasms
Whole Body Imaging*
Iodine
Therapeutic Uses
Thyroglobulin

Figure

• 

  Fig. 1 Representative 131I whole body scan images (A–C) with and (D) without star artifact after 1st 1.1 GBq of radioactive iodine treatment.

• 

  Fig. 2 Kaplan-Meier curves for recurrence-free survival between patients with and without star artifact (SA) in (A) total, (B) anti-thyroglobulin antibody (TgAb)-positive, (C) TgAb-negative and 1st stimulated thyroglobulin (sTg) ≤2 ng/mL, and (D) TgAb-negative and 1st sTg >2 ng/mL participants. Log-rank tests were done between two groups. 5YRR, 5-year recurrence rate; 10YRR, 10-year recurrence rate.

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