Letter: Diagnostic Whole-Body Scan May Not Be Necessary for Intermediate-Risk Patients with Differentiated Thyroid Cancer after Low-Dose (30 mCi) Radioactive Iodide Ablation (Endocrinol Metab 2014;29:33-9, Eon Ju Jeon et al.)

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Endocrinol Metab 2014;29:206-207

http://dx.doi.org/10.3803/EnM.2014.29.2.206 pISSN 2093-596X · eISSN 2093-5978

Letter

Diagnostic Whole-Body Scan May Not Be Necessary for

Intermediate-Risk Patients with Differentiated Thyroid

Cancer after Low-Dose (30 mCi) Radioactive Iodide Ablation

(

Endocrinol Metab

_{2014;29:33-9, Eon Ju Jeon et al.)}

Chan-Hee Jung

Division of Endocrinology and Metabolism, Department of Internal Medicine, Soonchunhyang University College of Medicine, Bucheon, Korea

The initial treatment of differentiated thyroid cancer (DTC) is thyroidectomy, followed by remnant ablation with radioiodine (I-131). However, substantial uncertainty persists over the in-dications and optimal dose for I-131. In addition, the useful-ness of a follow-up diagnostic I-131 whole-body scan (WBS) performed within 6 to 12 months after initial therapy is con-troversial [1]. Although a diagnostic WBS is not recommend-ed for low-risk patients, it may be of value in the follow-up of patients with high or intermediate risk [2]. Since incidence of DTC and patients who undergo remnant ablation has been in-creasing rapidly, these issues are interesting and important to clinicians. Jeon and Jung [3] demonstrated that a postablation diagnostic I-131 WBS in intermediate-risk patients with DTC may not be necessary. Although the authors suggested their study results carefully, in my opinion, below mentioned point need to be emphasized.

According to this study, among 255 intermediate-risk pa-tients, 233 had no I-131 uptake in the thyroid bed, and 22 had I-131 uptake on the thyroid bed. On diagnostic WBS, the group showing uptake had significantly higher lymph node metastasis and on average had stimulated thyroglobulin (TG) levels below 2 ng/mL in the absence of TG antibodies. Among

the 22 patients showing uptake in the thyroid bed, only five revealed stimulated TG levels above 2 ng/mL. Stimulated TG levels alone did not represent thyroid uptake in a significant portion of patients, and alone was not sufficient to screen pa-tients. Although the recurrence of thyroid cancer was not sta-tistically different between the group with no uptake and the group with uptake in the thyroid bed, the duration of follow-up was short. Moreover, only one among four patients with re-currence showed stimulated TG levels above 2 ng/mL and di-agnostic WBS showed no uptake in three patients with DTC recurrence. Prospective, long-term studies on whether patients with or without a thyroid remnant in diagnostic WBS show different prognoses and outcomes will provide important in-formation about this issue. Long-term follow-up data from 17 patients with thyroid bed uptake in this study is expected to provide important information despite the small number of pa-tients.

In real practice, the recommended preparatory low-iodine diet before diagnostic WBS is very stressful and bothersome for patients. Therefore, these results by Jeon and Jung [3] will be very valuable data in establishing an evidence-based fol-low-up strategy for DTC.

Corresponding author: Chan-Hee Jung,

Division of Endocrinology and Metabolism, Department of Internal Medicine, Soonchunhyang University College of Medicine, 170 Jomaru-ro, Wonmi-gu, Bucheon 420-767, Korea

Tel: +82-32-621-5158, Fax: +82-32-621-5016, E-mail: [email protected]

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Diagnostic WBS in Intermediate-Risk Patients with DTC.

207 CONFLICTS OF INTEREST

No potential conflict of interest relevant to this article was re-ported.

REFERENCES

1. Robbins RJ, Chon JT, Fleisher M, Larson SM, Tuttle RM. Is the serum thyroglobulin response to recombinant human thyrotropin sufficient, by itself, to monitor for residual thy-roid carcinoma? J Clin Endocrinol Metab 2002;87:3242-7.

2. American Thyroid Association (ATA) Guidelines

Task-force on Thyroid Nodules and Differentiated Thyroid Can-cer, Cooper DS, Doherty GM, Haugen BR, Kloos RT, Lee SL, Mandel SJ, Mazzaferri EL, McIver B, Pacini F, Sch-lumberger M, Sherman SI, Steward DL, Tuttle RM. Re-vised American Thyroid Association management guide-lines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid 2009;19:1167-214.