Radioiodine Remnant Ablation for Differentiated Thyroid Cancer: A Systematic Review and Meta-analysis

Radioactive Iodine Therapy in Differentiated Thyroid Cancer: Summary of the Korean Thyroid Association Guidelines 2024 from Nuclear Medicine Perspective, Part-II

Thyroid cancer, one of the most common endocrine tumors, generally has a favorable prognosis but remains a significant medical and societal concern due to its high incidence. Early diagnosis and treatment of differentiated thyroid cancer (DTC) significantly affect long-term outcomes, requiring the selection and application of appropriate initial treatments to improve prognosis and quality of life. Recent advances in technology and health information systems have enhanced our understanding of the molecular genetics of thyroid cancer, facilitating the identification of aggressive subgroups and enabling the accumulation of research on risk factors through big data. The Korean Thyroid Association (KTA) has revised the "KTA Guidelines on the Management of Differentiated Thyroid Cancers 2024" to incorporate these advances, which were developed by a multidisciplinary team and underwent extensive review and approval processes by various academic societies. This article summarizes the 2024 KTA guidelines for radioactive iodine (RAI) therapy in patients with DTC, written by the Nuclear Medicine members of the KTA Guideline Committee, and covers RAI therapy as initial management of DTC and RAI therapy in advanced thyroid cancer.

Standard operating procedure (SOP) for cervical ultrasound cine loop video sequences in the follow-up of differentiated thyroid carcinoma (DTC)

RATIONALE AND OBJECTIVES

Cervical ultrasound (US) is crucial in the follow-up of differentiated thyroid cancer (DTC). However, there are no guidelines for its acquisition and documentation, particularly concerning the role of additional video sequences, known as US cine loops (UCL). The aim of this study is to examine the clinical relevance (CR) of a new Standard Operating Procedure (SOP) for cervical UCL in DTC follow-up.

MATERIALS AND METHODS

A retrospective analysis was conducted on all UCL examinations of DTC follow-up patients at a tertiary care center between January 2010 and February 2018 to determine their clinical significance. The patients were divided into two groups: those with no documented CR (UCL-nCR) and those with documented CR (UCL-CR). The study reviewed the respective written medical US reports that were validated by experienced residents. The UCL-CR were categorized in: confirmation of a suspicious finding that was identified during conventional live US (UCL-CRcon), identification of a suspicious finding that was not identified during conventional live US (UCL-CRide), and invalidation of a suspicious finding that was identified during conventional live US (UCL-CRinv).

RESULTS

A total of 5512 UCLs in 652 DTC patients were analyzed, with 71.5% women and a mean age of 50 years. More than 90% of the tumors were low-risk at initial staging. The mean number of UCLs per patient was 8.5 ± 4.6. Overall, 95 cases of UCL-CR were identified in 82 patients (12.6%), with a patient-based number needed to scan of 8. UCL-CRinv was the most common type of UCL-CR, accounting for 77 (81.1%) of cases. The occurrences of 12 UCL-CRcon (12.6%) and 6 UCL-CRide (6.3%) were correspondingly less frequent. The diagnosis of UCL-CR was confirmed in 91.6% of cases during the clinical course.

CONCLUSIONS

In 12.6% of the patients, the additional acquisition and archiving of cervical UCL revealed clinical relevance in the course of DTC disease. The invalidation of suspicious findings through the retrospective analysis of former UCL occurred as the most significant benefit of this method. The UCL SOP can be easily and quickly integrated into the US workflow.

Influence of Radioiodine Therapy on Oral Health and Salivary Production in Patients With Differentiated Thyroid Carcinoma

OBJECTIVE

To evaluate the characteristics related to oral health and salivary production in patients with differentiated thyroid carcinoma (DTC) after radioiodine therapy (RIT).

METHODS

Cross-sectional study, which included patients with DTC after ablative and/or adjuvant RIT. Patients underwent assessment of oral health conditions, subjective assessment of xerostomia, and measurement of salivary flow. Salivary glands were assessed by cervical ultrasound at the time of clinical evaluation.

RESULTS

Sixty-seven DTC patients were included. Oral health was found very good or good in 60% of patients, 84% had no dental plaque or a slight amount, and 53% had normal-looking gums. There was a negative correlation between the salivary flow with activity of RIT ablative, number of RITs received, and total activity of radioiodine administered until oral assessment. Reduction in parotid gland volume on ultrasound was associated with greater number of times receiving RIT, longer time between RIT and patient assessment, greater 131I activity administered.

CONCLUSION

Good or very good oral health was observed in 60% of patients with DTC after RIT, 15% reported hyposalivation, and 13%, frequent xerostomia. Higher number and higher total activity of radioiodine administered, as well as reduction in the volume and heterogeneous texture of parotid gland on ultrasound were predictive factors of lower salivary flow.

Prognosis and ablation success in thyroid cancer: overcoming the challenges of incomplete clinical profiles

BACKGROUND

Differentiated thyroid carcinoma (DTC) is managed by surgery followed by radioiodine (RAI) therapy in most intermediate and high-risk patients. Most nonmetastatic patients have excellent treatment responses and have long-term disease-free status. A lack of comprehensive medical services in resource-limited nation leads to attrition of critical clinical prognostication information. This study aimed to identify readily available clinical, biochemical, and histopathological parameters to predict remnant ablation success and long-term outcomes.

METHODS

The study included DTC patients who underwent RAI after surgery. Ablation success was determined by thyroglobulin (Tg) and whole-body radioiodine scan. Patients were followed for at least 5 years to assess biochemical incomplete response (BIR) and structural recurrence.

RESULTS

The study included 383 patients (a mean age of 37.8 ± 12.9 years). Successful ablation was noted in 251 (65.5%). High preablative stimulated serum Tg (presTg), papillary variants, and central and lateral compartment lymph nodal metastases were associated with ablation failure. PresTg ( P  < 0.001) was the most significant predictor. After a 102.9 ± 34.5 months follow-up, 280 (73.1%) patients were disease-free. BIR and structural recurrence were noted in 103 and 32 patients. PresTg (8.1 ± 27.7 vs. 92.3 ± 99.9 ng/ml), ATg (112.9 ± 389.8 vs. 43.2 ± 89.8 IU/ml), papillary variant, central [109 (66.1%) vs. 56 (33.9%)], and lateral compartment [65 (63.7%) vs. 37 (36.3%) lymph nodal metastases were associated ( P  < 0.05) with BIR. PresTg >10.5 ng/ml has a sensitivity and specificity of 86.6 and 86.0% for predicting BIR. Patients with successful remnant ablation and a presTg level <10.5 ng/ml had a low risk of long-term disease recurrence (less than 5%).

CONCLUSION

This ambispective study found that successful ablation and long-term disease-free survival were achievable in a significant proportion of DTC patients. BIR (26.9%) and structural recurrence (8.4%) were not uncommon. PresTg levels emerged as a crucial predictor of ablation success and subsequent outcomes. In resource-limited regions, presTg levels and ablation failure can aid in optimizing treatment strategies and improving patient care.

Prise en charge des cancers thyroïdiens localisés de souche vésiculaire différenciée

MANAGEMENT OF LOCALIZED FOLLICULAR-DERIVED THYROID CANCER

The incidence of follicular-derived thyroid cancers has increased worldwide in recent decades, mainly papillary thyroid cancers at low recurrence risk. A process of de-escalation in the initial management and follow-up of these patients has therefore been implemented in parallel. This article provides the best practice recommendations made by the French learned societies (Société française d'endocrinologie, Société française de médecine nucléaire, Association française de chirurgie endocrine, Société française d'oto-rhino-laryngologie et de chirurgie de la face et du cou), european and international learned societies (European Society for Medical Oncology and the American Thyroid Association), in the management of follicular-derived thyroid cancer without distant metastases. The extent of thyroid surgery and lymph node dissection, strategies of radioiodine ablation, follow-up protocols and the management of excellent prognosis papillary cancers ≤ 10 mm will be addressed.

Comparing therapeutic outcomes: radioactive iodine therapy versus non-radioactive iodine therapy in differentiated thyroid cancer

Introduction

Radioactive iodine (RAI) has been utilized for nearly 80 years in treating both hyperthyroidism and thyroid cancer, and it continues to play a central role in the management of differentiated thyroid cancer (DTC) today. Recently, the use of RAI therapy for indolent, low-risk DTC has generated considerable debate. This case-control study evaluated the therapeutic response in DTC patients, comparing outcomes between those who received RAI therapy and those who did not.

Methods

The study included individuals diagnosed with either indolent or aggressive histological types of DTC who either underwent RAI therapy or did not. For each patient, information regarding demographics (age, sex, background), clinical data, laboratory parameters, pathological exam, history of RAI therapy, thyroid ultrasound findings, and loco-regional or distant metastasis was extracted. All group comparisons were made using a two-sided test at an α level of 5%.

Results

Out of 104 patients diagnosed with DTC, 76 met the inclusion criteria and were subsequently divided into two primary groups based on their history of RAI ablation. The majority of patients underwent RAI therapy (76.3%). Most patients had a good biochemical (68.4%, p = 0.246) and structural control (72.4%, p = 0.366), without a significant difference between the two groups. RAI therapy significantly protected against incomplete biochemical control in the overall population (p = 0.019) and in patients with histological indolent DTC (p = 0.030). Predictive factors for incomplete biochemical control included male sex (p = 0.008) and incomplete structural control (p = 0.002) across all patients, regardless of the histological type.

Discussions

While RAI therapy has traditionally been used to manage DTC, our study found no significant difference in biochemical and structural responses between patients who received RAI therapy and those who did not. However, RAI therapy emerged as a protective factor against incomplete biochemical control, even in histological indolent DTC cases. These findings suggest that while RAI therapy may not be universally necessary, it could be beneficial in reducing the risk of biochemical recurrence in select patient subgroups, such as those with incomplete structural control or male patients. Thus, a personalized approach to RAI therapy, tailored to individual risk factors, may improve patient outcomes without overtreatment.

Development of a predictive nomogram for intermediate-risk differentiated thyroid cancer patients after fixed 3.7GBq (100mCi) radioiodine remnant ablation

Objectives

The objective of this study was to develop a predictive nomogram for intermediate-risk differentiated thyroid cancer (DTC) patients after fixed 3.7GBq (100mCi) radioiodine remnant ablation (RRA).

Methods

Data from 265 patients who underwent total thyroidectomy with central lymph node dissection (CND) and received RRA treatment at a single institution between January 2018 and March 2023 were analyzed. Patients with certain exclusion criteria were excluded. Univariate and multivariate logistic regression analyses were performed to identify risk factors for a non-excellent response (non-ER) to RRA. A nomogram was developed based on the risk factors, and its performance was validated using the Bootstrap method with 1,000 resamplings. A web-based dynamic calculator was developed for convenient application of the nomogram.

Results

The study included 265 patients with intermediate-risk DTC. Significant differences were found between the ER group and the non-ER group in terms of CLNM>5, Hashimoto's thyroiditis, sTg level, TgAb level (P < 0.05). CLNM>5 and sTg level were identified as independent risk factors for non-ER in multivariate analysis. The nomogram showed high accuracy, with an area under the curve (AUC) of 0.833 (95% CI = 0.770-0.895). The nomogram's predicted probabilities aligned closely with actual clinical outcomes.

Conclusions

This study developed a predictive nomogram for intermediate-risk DTC patients after fixed 3.7GBq (100mCi) RRA. The nomogram incorporates CLNM>5 and sTg levels as risk factors for a non-ER response to RRA. The nomogram and web-based calculator can assist in treatment decision-making and improve the precision of prognosis information. Further research and validation are needed.

Correlation analysis between the quantitative parameters of iodine-131 single-photon emission computed tomography-computed tomography thyroid bed uptake and the efficacy of radioactive iodine adjuvant therapy for papillary thyroid cancer

Background

Single-photon emission computed tomography-computed tomography (SPECT/CT) quantification has emerged as a valuable tool for assessing disease prognosis by accurately identifying and characterizing abnormal lesions with accumulated radionuclides. Papillary thyroid carcinoma (PTC) is the most prevalent type of thyroid cancer, and radioactive iodine (RAI) therapy is a standard treatment following total thyroidectomy. This study aimed to explore the potential utility the quantitative parameters of the thyroid bed under iodine-131 (I-131) SPECT/CT in the efficacy of RAI adjuvant therapy for patients with PTC.

Methods

The retrospective cohort study enrolled 107 patients with PTC who underwent RAI adjuvant therapy from June 2020 to January 2023. Three days after the RAI adjuvant therapy, all patients underwent I-131 whole-body scans and SPECT/CT imaging. The quantitative parameters, including maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), and percent injected dose (%ID), were measured using image analysis software based on I-131 SPECT/CT thyroid bed uptake. Successful therapy was defined as inhibitory thyroglobulin (Tg) <0.2 ng/mL with negative thyroglobulin antibody (TgAb) and negative imaging examination 6 months after RAI adjuvant therapy. The relationship between the quantitative parameters and the treatment efficacy, in addition to the potential influencing factors, were analyzed.

Results

The quantitative parameters from the successful group [SUVmax: median 6.15 g/mL, interquartile range (IQR) 2.34-13.80 g/mL; SUVmean: median 2.02 g/mL, IQR 0.89-4.93 g/mL; %ID: median 2.00%, IQR 1.00-4.00%] were significantly lower than those from the unsuccessful group (SUVmax: median 19.03 g/mL, IQR 5.31-45.10 g/mL, SUVmean 4.64 g/mL, IQR 2.07-19.05 g/mL; %ID: median 8.00%, IQR 3.00-18.00%) (SUVmax: Z=-3.755; SUVmean; Z=-3.671; %ID: Z=-4.070; all P values <0.001). SUVmax, SUVmean and %ID were positively correlated with the stimulated thyroglobulin (sTg) and inhibitory Tg at 6 months after RAI adjuvant therapy, respectively (all P values <0.001). SUVmax [odds ratio (OR) =1.045], SUVmean (OR =1.130), and %ID (OR =1.092) were predictive factors for the failure of RAI adjuvant therapy (all P values <0.001).

Conclusions

Our study suggested that quantitative parameters (SUVmax, SUVmean, and %ID) derived from I-131 SPECT/CT imaging of the thyroid bed can serve as useful tools for predicting therapy outcomes following RAI adjuvant therapy.

Factors Affecting Ablation Success After I-131 Radioactive Iodine Therapy in Low and Intermediate Risk Papillary Thyroid Cancer

The study was to evaluate the effect of radioactive iodine (RAI) treatment application time and clinical, histopathological factors on ablation success in patients with operated papillary thyroid cancer (PTC) in low and intermediate-risk. One hundred sixty-one patients with PTC in the low and intermediate-risk were evaluated. Most patients (89.4%) were in the low-risk, and 10.6% were in the intermediate-risk. When the patients were divided into two groups according to the date of receiving RAI treatment after surgery, those who received early treatment (≤3 months) constituted the majority of the patients (72.7%). Seventeen patients received 1.85 Gigabecquerel (GBq), 119 3.7 GBq, 25 5.55 GBq RAI. Most patients (82%) achieved ablation success after the first RAI treatment. The time interval between surgery and RAI treatment did not affect ablation success. Stimulated Tg level measured on the RAI treatment day was an independent predictive factor for successful ablation (p<0.001). The cut-off value of Tg found to predict ablation failure was 5.86 ng/ml. It was concluded that 5.55 GBq RAI treatment could predict ablation success compared to 1.85 GBq dose (p=0.017). It was concluded that having a T1 tumor may predict treatment success compared to a T2 or T3 tumor (p=0.001, p<0.001, retrospectively). The time interval does not affect ablation success in low and intermediate-risk PTC. The ablation success rate may decrease in patients who receive low-dose RAI and have high Tg levels before treatment. The most crucial factor in achieving ablation success is giving enough doses of RAI to ablate the residual tissue.

Could Oxidative Stress Play a Role in the Development and Clinical Management of Differentiated Thyroid Cancer?

Increased oxidative stress (OS) has been implicated as a relevant risk factor for cancer progression. Furthermore, patients diagnosed with differentiated thyroid cancer (DTC) have been characterized by an increased OS status. Therefore, assessing OS status could potentially be considered a useful tool in DTC clinical management. This measurement could be particularly valuable in personalizing treatment protocols and determining new potential medical targets to improve commonly used therapies. A literature review was conducted to gather new information on DTC clinical management, with a particular focus on evaluating the clinical utility of OS. These meta-analyses concentrate on novel approaches that employ the measurement of oxidative-antioxidant status, which could represent the most promising area for implementing clinical management.

Recurrent Differentiated Thyroid Cancer: The Current Treatment Options

Differentiated thyroid carcinomas (DTC) have an excellent prognosis, but this is sometimes overshadowed by tumor recurrences following initial treatment (approximately 15% of cases during follow-up), due to unrecognized disease extent at initial diagnosis or a more aggressive tumor biology, which are the usual risk factors. The possible sites of recurrence are local, regional, or distant. Local and regional recurrences can usually be successfully managed with surgery and radioiodine therapy, as are some isolated distant recurrences, such as bone metastases. If these treatments are not possible, other therapeutic options such as external beam radiation therapy or systemic treatments should be considered. Major advances in systemic treatments have led to improved progression-free survival in patients previously considered for palliative treatments; among these treatments, the most promising results have been achieved with tyrosine kinase inhibitors (TKI). This review attempts to give a comprehensive overview of the current treatment options suited for recurrences and the new treatments that are available in cases where salvage surgery is not possible or in cases resistant to radioiodine.

[Modern aspects influencing the management of patients with papillary thyroid cancer]

Thyroid cancer (TC) is the most common malignant tumor of the endocrine glands and accounts to 3% of the total structure of oncological morbidity. Papillary thyroid cancer (PTC) is the most common histological variant of thyroid malignancies. It accounts for about 85% of all cases of thyroid cancer. Despite good postoperative results and excellent survival compared to many other malignancies, tumor metastases to the paratracheal lymph nodes are quite common. This review of the literature considers the current personalized approach to patients with papillary thyroid cancer and current aspects influencing the management of patients with PTC.

Correlation analysis of I-131 SPECT/CT uptake parameters with the success ablation treatment of thyroid remnant in patients with low-intermediate-risk differentiated thyroid cancer

OBJECTIVE

To predict the successful outcome of radioactive iodine-131 (I-131) ablation treatment for differentiated thyroid cancer (DTC) patients using quantitative parameters from therapeutic I-131 SPECT/CT.

METHODS

This retrospective study enrolled 145 DTC patients (41 males and 104 females) who had radioactive iodine-131 (I-131) (RAI) ablation therapy following thyroidectomy surgery from July 2020 to May 2021. The median age was 47 years (24-65 years). All the patients underwent therapeutic I-131 thyroid SPECT/CT scan after RAI ablation. The I-131 uptake quantitative parameters SUV max , SUV mean %ID and ∆Tg (defined as the Tg level before RAI ablation minus the Tg level after six months) were assessem. Successful ablation treatment was defined as the level of TSH-stimulated Tg≤1 ng/mL and the disappearance of the thyroid bed on a whole-body I-131 scan six months or later after ablation treatment.

RESULTS

The quantitative parameters from therapeutic I-131 SPECT/CT of the successful ablation (n=130) group with SUV max 7.74 (3.84, 18.78) g/ml, SUV mean 4.02 (2.11, 6.39) g/ml and %ID 2.21% (0.67%, 7.30%) were significantly higher than those of the unsuccessful (n=15) group 0.75 (0.53, 1.28) g/ml, 0.44 (0.29, 0.79) g/ml and 0.16% (0.06%, 1.48%) (Z=-5.87, -5.71 and -4.99, all P < 0.001). SUV max , SUV mean and %ID were positively correlated with ΔTg (all P < 0.001). Receiver operating characteristics curve analysis showed that %ID performed better predict value than either SUV max (AUC=0.914, and 0.874, P=0.009) or SUV mean (AUC= 0.863 P=0.002). SUV max , SUV mean and%ID (OR =1.50, 2.85 and 1.01 all P < 0.001) were all independent predictors of successful RAI ablation.

CONCLUSION

The quantitative parameters of therapeutic I-131 SPECT/CT were related to the efficacy of ablation treatment, and %ID could predict the successful outcome of ablation treatment for DTC patients.

Strategies for Radioiodine Treatment: What’s New

Radioiodine treatment (RAI) represents the most widespread and effective therapy for differentiated thyroid cancer (DTC). RAI goals encompass ablative (destruction of thyroid remnants, to enhance thyroglobulin predictive value), adjuvant (destruction of microscopic disease to reduce recurrences), and therapeutic (in case of macroscopic iodine avid lesions) purposes, but its use has evolved over time. Randomized trial results have enabled the refinement of RAI indications, moving from a standardized practice to a tailored approach. In most cases, low-risk patients may safely avoid RAI, but where necessary, a simplified protocol, based on lower iodine activities and human recombinant TSH preparation, proved to be just as effective, reducing overtreatment or useless impairment of quality of life. In pediatric DTC, RAI treatments may allow tumor healing even at the advanced stages. Finally, new challenges have arisen with the advancement in redifferentiation protocols, through which RAI still represents a leading therapy, even in former iodine refractory cases. RAI therapy is usually well-tolerated at low activities rates, but some concerns exist concerning higher cumulative doses and long-term outcomes. Despite these achievements, several issues still need to be addressed in terms of RAI indications and protocols, heading toward the RAI strategy of the future.

Association Between Radioactive Iodine Treatment for Pediatric and Young Adulthood Differentiated Thyroid Cancer and Risk of Second Primary Malignancies

PURPOSE

Since the 1980s, both the incidence of differentiated thyroid cancer (DTC) and use of radioactive iodine (RAI) treatment increased markedly. RAI has been associated with an increased risk of leukemia, but risks of second solid malignancies remain unclear. We aimed to quantify risks of second malignancies associated with RAI treatment for DTC in children and young adults, who are more susceptible than older adults to the late effects of radiation.

METHODS

Using nine US SEER cancer registries (1975-2017), we estimated relative risks (RRs) for solid and hematologic malignancies associated with RAI (yes v no or unknown) using Poisson regression among ≥ 5- and ≥ 2-year survivors of nonmetastatic DTC diagnosed before age 45 years, respectively.

RESULTS

Among 27,050 ≥ 5-year survivors (median follow-up = 15 years), RAI treatment (45%) was associated with increased risk of solid malignancies (RR = 1.23; 95% CI, 1.11 to 1.37). Risks were increased for uterine cancer (RR = 1.55; 95% CI, 1.03 to 2.32) and nonsignificantly for cancers of the salivary gland (RR = 2.15; 95% CI, 0.91 to 5.08), stomach (RR = 1.61; 95% CI, 0.70 to 3.69), lung (RR = 1.42; 95% CI, 0.97 to 2.08), and female breast (RR = 1.18; 95% CI, 0.99 to 1.40). Risks of total solid and female breast cancer, the most common cancer type, were highest among ≥ 20-year DTC survivors (RR_solid = 1.47; 95% CI, 1.24 to 1.74; RR_breast = 1.46; 95% CI, 1.10 to 1.95). Among 32,171 ≥ 2-year survivors, RAI was associated with increased risk of hematologic malignancies (RR = 1.51; 95% CI, 1.08 to 2.01), including leukemia (RR = 1.92; 95% CI, 1.04 to 3.56). We estimated that 6% of solid and 14% of hematologic malignancies in pediatric and young adult DTC survivors may be attributable to RAI.

CONCLUSION

In addition to leukemia, RAI treatment for childhood and young-adulthood DTC was associated with increased risks of several solid cancers, particularly more than 20 years after exposure, supporting the need for long-term surveillance of these patients.

Radioactive iodine in low- to intermediate-risk papillary thyroid cancer

It remains controversial whether papillary thyroid cancer (PTC) patients with low- to intermediate-risk disease should receive radioactive iodine (RAI) after total thyroidectomy (TT). We aim to identify those who might benefit from RAI treatment in PTC patients with cervical nodal metastasis after TT. Patients were divided into TT and TT+RAI groups from the Surveillance, Epidemiology, and End Results (SEER) database (2004-2018). Overall survival (OS) and cancer-specific survival (CSS) were compared, and propensity score matching (PSM) was performed between groups. A total of 15,179 patients were enrolled, including 3,387 (22.3%) who underwent TT and 11,792 (77.7%) who received TT+RAI. The following characteristics were more likely to present in the TT+RAI group: multifocality, capsular extension, T3, N1b, and more metastatic cervical lymph nodes. RAI was associated with better OS in low- to intermediate-risk PTC patients in the multivariate Cox regression model. The subgroup analysis showed that RAI predicted better OS in patients ≥55 years, American Joint Committee on Cancer (AJCC) stage II, and capsular extension with a hazard ratio (HR) (95% CI) of 0.57 (0.45-0.72), 0.57 (0.45-0.72), and 0.68 (0.51-0.91), respectively. However, RAI failed to improve the prognoses of patients with age <55 years, AJCC stage I, PTC ≤1 cm, and capsular invasion. In the PSM cohort with 3,385 paired patients, TT+RAI treatment predicted better OS compared with TT alone. In addition, TT+RAI predicted better OS in patients with metastatic cervical lymph nodes ≥2, multifocality, extracapsular extension, and American Thyroid Association (ATA) intermediate risk. In conclusion, RAI was associated with better OS in low- to intermediate-risk PTC patients with age ≥55 years, multifocality, extrathyroidal extension, and ATA intermediate risk. However, the survival benefit from RAI may be limited in patients with AJCC stage I, PTC ≤1 cm, unifocality, capsular invasion, and ATA low-risk diseases; these patients even showed pathological cervical lymph node metastasis.