Could short thyroid hormone withdrawal be an effective strategy for radioiodine remnant ablation in differentiated thyroid cancer patients?
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Current guidelines recommend thyroid hormone withdrawal (THW) of 3–4 weeks before radioiodine remnant ablation (RRA) of differentiated thyroid carcinoma (DTC). We aimed to evaluate (1) the reliability of a shorter THW (i.e., 14 days) to achieve adequate TSH levels (i.e., 30 mU/l), (2) the association between length of THW and response to therapy, and (3) the potential association between pre-ablation TSH levels and patients’ outcome.
After thyroidectomy, all patients started LT4 therapy, which was subsequently discontinued in order to perform RRA. Patients were broken down into two groups according to the length of THW: group A, 2 weeks of THW, and group B, 3–4 weeks of THW. We used clinical, biochemical, and imaging data to evaluate patients’ outcome. By means of univariate and multivariate analysis, including main DTC prognostic factors, we assessed the impact of THW length and TSH levels on patients’ outcome.
We evaluated 222 patients, 85 of whom were treated with RRA after a THW period of 2 weeks (group A). All other 137 patients underwent RRA after 3–4 weeks THW (group B). At the time of RRA all patients presented TSH levels ≥30 mU/l. After a median follow-up time of 3.4 years, we found 183 patients (82%) with excellent response to treatment and 39 patients (18%) showing incomplete response. Kaplan–Meier response to therapy curves showed that ablation-Tg, tumor size, and lymph node status were significantly associated with prognosis; no associations were found between THW length, TSH levels, and prognosis. Multivariate Cox model showed that only ablation-Tg was significantly associated with treatment response.
Prior to RRA, a short 2-week THW is an effective method to stimulate TSH levels. No difference in terms of incomplete response to treatment was observed between DTC patients prepared for RRA with a short THW and those with the long THW.
KeywordsDifferentiated thyroid cancer TSH stimulation Radioactive remnant ablation Prognosis
This research did not receive any specific grants from any funding agency in the public, commercial, or non-profit sectors.
Compliance with ethical standards
Conflict of interest
The authors have no conflicts of interest disclose.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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