Abstract
BackgroundTotal thyroidectomy (TT) or lobectomy without radioactive iodine (RAI) is becoming a common management for patients with low-risk differentiated thyroid cancer (DTC). However, the assessment of response to therapy for these patients remains controversial. The aim of this study was to propose and validate a new dynamic evaluation strategy to assess the response to therapy in patients with low-risk DTC treated with TT or lobectomy but without RAI.MethodsWe performed a retrospective analysis of 543 adult patients with low-risk DTC who underwent TT or lobectomy without RAI therapy. Follow-up consisted of trends of serum thyroglobulin (Tg), anti-thyroglobulin antibody (TgAb) levels and neck ultrasonography (US) were conducted every 6–24 months. Response to therapy assessments were defined as excellent response, biochemical incomplete response, structural incomplete response, and indeterminate response according to the follow-up findings.ResultsAt a median follow-up of 51 months (range 33–66 months), 517 (95%) had excellent response, while the other 26 had either biochemical incomplete response (an increasing trend of suppressed serum Tg levels, n=9; an increasing trend of TgAb levels, n=3) or indeterminate response (a stable or decreasing trend of suppressed serum Tg levels, but a stable positive trend of TgAb levels, n=14). No patients had structural incomplete response or no deaths related to thyroid cancer. The risk of incomplete response was significantly higher in lobectomy than in TT (p<0.001).ConclusionOur study proposed and validated a new dynamic response to therapy assessment depending on trends of suppressed serum Tg, TgAb levels, and neck US findings which could be an appropriate tool for postoperative follow-up in low-risk DTC patients without RAI therapy. Our findings provided further evidence to support no routine recommendation of RAI after surgery in low-risk DTC.
Highlights
The prevalence of low-risk differentiated thyroid cancer (DTC) is increasing significantly, which mainly due to the early diagnosis of thyroid microcarcinoma (TMC) by using neck ultrasonography (US) [1,2,3,4]
Optimal management of DTC usually requires interdisciplinary cooperation, including surgery, risk-adapted postoperative radioactive iodine (RAI) therapy, individualized thyroid hormone therapy, and follow-up for the detection of patients with persistent or recurrent disease [5,6,7]. Considering factors such as the excellent prognosis of low-risk DTC [5, 8], absence of significant reduction in recurrence rate or disease-free survival in low-risk patients treated with RAI [9, 10], scarce evidence concerning the usefulness of RAI in improving disease-specific mortality in low-risk DTC [5], and potential side effects on RAI [e.g., chronic sialadenitis [11, 12], secondary malignancies [13, 14]], the 2015 American Thyroid Association (ATA) guidelines recommend performing conservative strategies, namely, total thyroidectomy (TT) or lobectomy without RAI ablation, for low-risk DTC patients [5]
The inclusion criteria were as follows: patients aged >18 years at the time of surgery; patients with documented low-risk DTC who underwent lobectomy with isthmusectomy or TT, and/or central/lateral neck dissection, without RAI remnant ablation therapy, with thyroid-stimulating hormone (TSH) suppressive therapy; and those who were routinely followed up every 6–24 months with the determination of serum TSH, Tg and thyroglobulin antibody (TgAb) levels and neck US findings
Summary
The prevalence of low-risk differentiated thyroid cancer (DTC) is increasing significantly, which mainly due to the early diagnosis of thyroid microcarcinoma (TMC) by using neck ultrasonography (US) [1,2,3,4]. In 2016, Momesso et al proposed a dynamic risk stratification method (mainly based on neck US findings and different suppressed serum Tg cutoff values, namely, Tg 5 ng/mL for TT; Tg 30 ng/mL for lobectomy, to stratify assessments as excellent response, indeterminate response, biochemical incomplete response and structural incomplete response) to evaluate the response to initial surgery in low-risk DTC patients who did not undergo RAI therapy [15].
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