Rojas, Tatiana

Background: Preparation for radioiodine (RAI) therapy in differentiated thyroid cancer (DTC) often requires thyroid hormone withdrawal (THW) to achieve thyrotropin (TSH) stimulation. Current guidelines recommend TSH ≥30 mIU/L, a target that prolongs hypothyroidism and worsens quality of life, yet rests on limited evidence. Objective: To evaluate the association between pre-RAI TSH levels and oncologic outcomes in adults with DTC prepared by THW. Methods: We conducted a systematic review and meta-analysis of studies comparing outcomes across pre-RAI TSH thresholds (<30 vs. ≥30, <60 vs. ≥60, and <90 vs. ≥90 mIU/L) in adults with DTC prepared by THW. Primary outcomes included disease-specific mortality, recurrence, and response to therapy. Searches in MEDLINE, Embase, Cochrane, and Scopus (inception to March 2025) identified eligible studies. Risk of bias was assessed using the CLARITY tool and certainty of evidence using GRADE. Pooled relative risks (RRs) were calculated using random-effects models. This systematic review was registered in PROSPERO (CRD42020158354). Results: This meta-analysis included eight retrospective cohort studies comprising a total of 4651 DTC patients, predominantly women (68.5%) with a mean age of 46 years. All patients underwent THW before RAI. Across all TSH thresholds examined (<30, <60, and <90 mIU/L), higher pre-RAI TSH levels were not associated with better treatment response, lower recurrence, or reduced mortality. Specifically, patients with higher pre-RAI TSH levels (≥30 mIU/L) did not have better oncologic outcomes compared with those with lower levels (<30 mIU/L). At 2- and 3-year follow-up, no significant differences were observed in excellent (pooled RR = 0.87; confidence interval [CI] 0.68–1.11) or indeterminate (RR = 1.28; CI 0.72–2.27) response rates. Similarly, recurrence rates did not differ (RR = 1.45; CI 0.83–2.55), and no study demonstrated a difference in disease-specific mortality across follow-up periods extending up to 10 years. The certainty of evidence for all outcomes was rated very low due to risk of bias, heterogeneity, and imprecision. Conclusions: The current evidence base is insufficient to support or refute the routine use of a specific TSH threshold before RAI administration. These findings question the recommendation to achieve TSH ≥30 mIU/L before RAI and highlight the need for trials to define the minimal effective level of TSH stimulation.

Introduction Differentiated thyroid cancer (DTC) is the most common endocrine malignancy, with a high 5-year survival rate of approximately 98%. Despite advances in diagnosis and treatment, up to 20% of patients experience recurrence, adversely affecting their quality of life. Predictive models have been developed to assess recurrence risk and guide clinical decision-making, but these models often face limitations such as retrospective design, lack of diversity in study populations and absence of external validation. The primary aim is to externally validate existing predictive models for DTC recurrence using prospective data from a diverse Latin American cohort. The secondary aim is to explore opportunities for model recalibration to improve their performance in our population. Methods and analysis The CaTaLiNA study is a multicentre prospective observational study conducted across 10 hospitals in five Latin American countries, including Ecuador, Peru, Uruguay and Mexico. Patients aged 18 years or older receiving treatment for DTC, such as the first thyroid surgery, active surveillance or radiofrequency ablation will be included. Recruitment will occur from November 2023 to June 2025, with follow-up extending until June 2028. Data collection will include baseline clinical, surgical and histological characteristics, treatment details and follow-up outcomes. Statistical analysis will follow the Transparent Reporting of a multivariable prediction model for Individual Prognosis or Diagnosis guidelines, using imputation strategies for missing data and evaluating calibration and discrimination of the prediction models. Calibration measures include the ratio of expected and observed events, calibration slope and calibration plot, while discrimination will be assessed using the C-index and area under the receiver operating characteristic curve. Ethics and dissemination This study protocol was approved by Comité de Ética de Investigación en Seres Humanos de la Universidad San Francisco de Quito USFQ ‘CEISH-USFQ’ APO-010–2023-CEIHS-USFQ Oficio No. 161-2023-CA-23030M-CEISH-USFQ. Results will be disseminated via peer-reviewed publications.

SAGE-Journals-Accessible-Video-Player 10.1089/ve.2021.0032.M1 sj-vid-1-vde-10.1089_ve.2021.0032

Abstract Background: Patients with differentiated thyroid cancer (DTC) may benefit of radioiodine ablation (RAI) to reduce the probability of thyroid cancer recurrence. Guidelines recommend that thyroid stimulating hormone (TSH) of &gt;30mIU/L before RAI to optimize treatment response. However, evidence regarding this recommendation is conflicting. We conducted a systematic review and meta-analysis to compare outcomes (thyroid cancer recurrence and survival at 10 years of follow up) of stimulated TSH threshold before RAI with primary analysis focus on &lt;30 mIU/L versus ≥30 mIU/L, and subgroup analysis on &lt;90 mIU/L versus ≥90 mIU/L in patients with DTC after initial total thyroidectomy. Methods: The protocol for this study is registered and available online (CRD42020158354). Briefly, we searched several databases from their inception to April 2020. Reviewers, working independently and in duplicate selected studies for inclusion, extracted data, and evaluated each study’s risk of bias. We excluded studies that used recombinant human thyroid stimulating hormone before ablation. Results: We included five retrospective cohort studies, which enrolled a total of 2,514 patients. Risk of bias was low in four studies and high in one study. Mean age was 47 years old (ranged from 40.7 to 47.9) and most of them were female (69%). The most common DTC type was papillary thyroid cancer (78%). From those articles that reported tumor characteristics, 48% had a size ≤2cm (T1b) and 47% &gt;2cm. Moreover, 73% of the patients had no regional lymph metastasis (N0). Two studies reported radioiodine mean dose given of 30 and 100 mci. A total of 301 patients were included in the TSH threshold &lt;30 mIU/L group and 1788 patients in the TSH ≥30 mIU/L group. Comparing stimulated TSH threshold before RAI (&lt;30 mIU/L versus ≥30 mIU/L), there was difference in recurrence at 1 year (RR 2.46 (C.I. 1.09-5.55) and at 20 years (RR 1.71 (C.I. 1.19 – 2.47). However, there was no difference in mortality at 20 years (RR 0.53 (Confidence Interval (C.I.) 0.12-2.23). In addition, 10-years recurrence was not different when we compared &lt;90 mIU/L versus ≥90 mIU/L TSH (RR 1.06; 95%CI: 0.88 – 1.27). Conclusions: Mortality do not differ between recommended TSH goal (≥30 mIU/L) vs &lt;30 mIU/L in thyroid hormone withdrawal-aided radioiodine ablation in DTC patients. However, the risk of recurrence is reduced when patients achieved a TSH level &gt;30 UI/mL. These results suggest that patients may need to reach a stimulated TSH ≥30 mIU/L stimulated TSH threshold to be treated. Randomized trials are needed to confirm these findings.