Low-Activity Radioactive Iodine Therapy for Thyroid Carcinomas Exhibiting Nodal Metastases and Extrathyroidal Extension May Lead to Early Disease Recurrence

The Definition of Recurrence of Differentiated Thyroid Cancer: A Systematic Review of the Literature

Background: Recurrence is a key outcome to evaluate the treatment effect of differentiated thyroid carcinoma (DTC). However, no consistent definition of recurrence is available in current literature or international guidelines. Therefore, the primary aim of this systematic review was to delineate the definitions of recurrence of DTC, categorized by total thyroidectomy with radioactive iodine ablation (RAI), total thyroidectomy without RAI and lobectomy, to assess if there is a generally accepted definition among these categories. Methods: This study adhered to the 2020 Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. In December 2023, a systematic literature search in MEDLINE and EMBASE was performed for studies reporting on the recurrence of DTC, from January 2018 to December 2023. Studies that did not provide a definition were excluded. Primary outcome was the definition of recurrence of DTC. Secondary outcome was whether studies differentiated between recurrence and persistent disease. Two independent investigators screened the titles and abstracts, followed by full-text assessment and data extraction. The study protocol was registered in PROSPERO, CRD42021291753. Results: In total, 1450 studies were identified. Seventy studies met the inclusion criteria, including 69 retrospective studies and 1 randomised controlled trial (RCT). Median number of patients in the included studies was 438 (range 25-2297). In total, 17 studies (24.3%) reported on lobectomy, 4 studies (5.7%) on total thyroidectomy without RAI, and 49 studies (70.0%) with RAI. All studies defined recurrence using one or a combination of four diagnostic modalities cytology/pathology, imaging studies, thyroglobulin (-antibodies), and a predetermined minimum tumor-free time span. The most common definition of recurrence following lobectomy was cytology/pathology-proven recurrence (47.1% of this subgroup), following total thyroidectomy with RAI was cytology/pathology-proven recurrence and/or anomalies detected on imaging studies (22.4% of this subgroup). No consistent definition was found following total thyroidectomy without RAI. Nine studies (12.9%) differentiated between recurrence and persistent disease. Conclusion: Our main finding is that there is no universally accepted definition for recurrence of DTC in the current studies across any of the treatment categories. The findings of this study will provide the basis for a future, international Delphi-based proposal to establish a universally accepted definition of recurrence of DTC. A uniform definition could facilitate global discussion and enhance the assessment of treatment outcomes regarding recurrence of DTC.

Controversies in the Management of Intermediate-Risk Differentiated Thyroid Cancer

BACKGROUND

Intermediate-risk thyroid cancer accounts for up to two-thirds of all cases of differentiated thyroid cancer (DTC), yet it is subject to substantial variations in risk stratification and management strategies.

METHODS

This comprehensive review examines the current controversies regarding diagnosis and management of intermediate risk DTC.

RESULTS

The evolution of risk stratification systems is discussed, highlighting limitations such as heterogeneity in patient cohorts, variability in outcome definitions, and the need for more precise risk estimation tools incorporating genetic profiles and individual risk modifiers. The role of radioactive iodine therapy in intermediate-risk DTC is examined, considering evolving evidence, conflicting study results, and the necessity for personalized treatment decisions based on risk modifiers, potential morbidity, and patient preferences. Furthermore, the shift from total thyroidectomy to lobectomy in certain intermediate-risk cases is explored, emphasizing the need for tailored surgical approaches and the impact on long-term outcomes, recurrence rates, and quality of life.

CONCLUSION

Management of intermediate-risk DTC remains controversial. This review summarizes current evidence to aid decision-making. Further research, prospective trials, and collaboration are crucial to address these complexities and personalize care for patients.

Radioiodine therapy in the different stages of differentiated thyroid cancer

Differentiated thyroid cancer is the most frequent type of thyroid cancer with an increasing incidence in the last decades. The initial management is represented by surgical treatment followed by radioactive iodine therapy that includes remnant ablation, adjuvant treatment or treatment of metastatic disease. Radioactive iodine treatment is performed only in selected cases based on the risk of recurrence and mortality during follow up, according to American Joint Committee on Cancer Union for international Cancer Control Tumor, Node, Metastasis (AJCC/TNM) staging system and the 2015 American Thyroid Association (ATA) risk stratification system. This article will review the key factors to consider when planning radioactive iodine therapy in differentiated thyroid cancer patients after surgery and during follow up.

Adjuvant I-131 therapy for T0-3 N1b M0 differentiated thyroid cancer with many (≥ 5) positive nodes

Background

In patients with well-differentiated thyroid cancer, there is controversy about the prognostic importance of a large number of positive neck nodes and the potential value of radioiodine therapy. The purpose of this study was to evaluate this issue in the group of patients for whom it is most clinically important - those with classic histology and favorable T and M stage.

Materials and methods

Twenty-five patients met the following inclusion criteria: classic histology of papillary or follicular thyroid carcinoma treated with total thyroidectomy and neck dissection followed by adjuvant I-131 treatment in our department between January 1, 2003, and December 31, 2013; adult age of > 21 years; and American Joint Committee on Cancer (AJCC ) stage (8^th edition) of T0-3, N1b with ≥ 5 positive nodes, and M0.

Results

The median positive node number was 10 (range, 5-31). The median adjuvant I-131 dose was 158 mCi (range, 150-219 mCi). The median follow-up in patients without recurrence after treatment was 7.3 years. The 10-year actuarial rates were favorable: overall survival, 100%; freedom from visible recurrence, 82%; and visible or biochemical recurrence, 72%.

Conclusion

Recurrence was infrequent in our study population with ≥ 5 positive nodes following moderate-dose adjuvant I-131 treatment. These results are valuable in directing initial adjuvant therapy and follow-up intensity. Our results do not inform the question of the use of postoperative thyroglobulin (Tg) level to select N1b patients for low-dose I-131 treatment.

Assessing Diagnostic Value of Combining Ultrasound and MRI in Extrathyroidal Extension of Papillary Thyroid Carcinoma

Purpose

To explore the separate diagnostic value of preoperative ultrasound (US), magnetic resonance imaging (MRI), and the combination of US and MRI in extrathyroidal extension (ETE) of papillary thyroid carcinoma (PTC).

Materials and Methods

This retrospective study was approved by the Affiliated People’s Hospital of Jiangsu University review board. A total of 158 PTC patients with ETE received preoperative US and MRI examination and underwent surgery between May 2014 and December 2018 in Affiliated People’s Hospital of Jiangsu University. For each case, the US and MRI features of ETE were retrospectively and independently investigated by two radiologists. The clinical assessment for each case was implemented, respectively, using US imaging only, MRI only, and a combination of both modalities at three different time points with one-month intervals.

Results

The diagnostic accuracies of US, MRI, and the combined set for T3 (minimal ETE) were 91.7% (88/96), 74.0% (71/96), and 97.9% (94/96), respectively, indicating a significantly different performance (P < 0.001). The diagnostic accuracies for T4 (extensive ETE) were 62.9% (39/62), 87.1% (54/62), and 93.5% (58/62), respectively. The difference between the three methods for T4 was statistically significant (P = 0.000). The diagnostic accuracies for overall ETE were 80.4% (127/158), 79.1% (125/158), and 96.2% (152/158), respectively. The difference between the three methods for ETE was statistically significant (P = 0.001).

Conclusion

This study suggests that ETE can be predicted most accurately by the combination of preoperative US and MRI.

Can Diffusion-Weighted MR Imaging Be Used as a Tool to Predict Extrathyroidal Extension in Papillary Thyroid Carcinoma?

RATIONALE AND OBJECTIVES

To evaluate whether quantitative diffusion-weighted MR imaging (DWI) with multi-b values can be used as a tool to predict the aggressiveness by using the histological feature of extrathyroidal extension (ETE) in papillary thyroid carcinoma (PTC).

MATERIALS AND METHODS

238 patients were pathologically confirmed as PTCs underwent preoperative multi-b value DWI (300, 500, and 800 s/mm²) between January 2015 and December 2017. The patients were divided into three groups according to the degree of ETE: without ETE, minimal ETE, and extensive ETE. The apparent diffusion coefficients (ADCs) were evaluated for three different b values (b = 300 s/mm², b = 500 s/mm², and b = 800 s/mm²). The ADC values of the groups with and without ETE, minimal and extensive ETE were compared. The diagnostic relevance of the ADC values in terms of predicting ETE was compared using a receiver operating characteristic analysis. Differences between the areas under the curves (AUCs) were compared by using a Delong test.

RESULTS

PTCs with ETE had significantly lower ADC₃₀₀, ADC₅₀₀ and ADC₈₀₀ values than PTCs without ETE (p = 0.001, p < 0.001, and p < 0.001, respectively). The AUC of the mean ADC₅₀₀ value (0.905) was higher than that of the ADC₃₀₀ and ADC₈₀₀ values (0.607 and 0.770, respectively) in differentiating ETE from without ETE (p < 0.001). The cut-off value of ADC₅₀₀ to discriminate PTCs with and without ETE was determined at 1.407 × 10^-3 mm²/s, with sensitivity of 80.7%, specificity of 86.7%, and an AUC of 0.905.

CONCLUSION

The ADC value can be demonstrated an effective tool for evaluating the aggressiveness with the histological feature of ETE in PTC. In particular, ADC value at b = 500 s/mm² showed the best performance for noninvasive preoperative evaluation of ETE.

Can patients with papillary thyroid carcinoma and low postoperative thyroglobulin in the presence of clinically apparent lymph node metastases (cN1) be spared from radioiodine?

BACKGROUND

The study evaluated the recurrence rate in patients with papillary thyroid carcinoma (PTC) and clinically apparent lymph node metastases (LNM) (cN1) who had low thyroglobulin (Tg) after total thyroidectomy and who were not submitted to adjuvant therapy with ¹³¹I.

METHODS

This was a prospective study. It included 82 cN1 patients (≤3 LNM ≤1.5 cm without macroscopic extracapsular extension) with tumors ≤4 cm without macroscopic extrathyroid invasion (T1-2) and who after thyroidectomy had unstimulated Tg (u-Tg) < 0.3 ng/ml, negative antithyroglobulin antibodies (TgAb), and neck ultrasonography (US) showing no anomalies. The patients were not submitted to therapy with ¹³¹I.

RESULTS

The time of follow-up ranged from 24 to 156 months (median 84 months). Seventy-nine patients (96.3%) continued to have u-Tg < 0.3 ng/ml and negative US. Three patients (3.6%) exhibited an increase in Tg and structural recurrence was detected in two. After treatment, these patients achieved u-Tg < 1 ng/ml and the imaging methods revealed no apparent tumor.

CONCLUSIONS

The results suggest that even cN1 patients, given the absence of extensive LNM or other adverse findings, who have low Tg and neck US showing no anomalies after thyroidectomy do not require radioiodine.

Postoperative thyroid remnants for differentiated thyroid cancer may not affect the outcome of high-dose radioiodine therapy

OBJECTIVES

This study aims to provide a way to estimate the volume of the thyroid remnant and determine its relationship with the outcome of radioiodine (RAI) therapy in depth.

MATERIALS AND METHODS

A retrospective analysis was performed on patients who underwent initial RAI therapy between January 2010 and January 2016. The patients were divided into five groups based on the thyroid remnant estimated by post-therapy whole-body scan(post-Rx WBS), thyroid scintigraphy and ultrasonography. The relationship between the volume of thyroid remnant and the outcome of RAI therapy were evaluated by univariate analysis and multivariate analysis.

RESULTS

Of 703 patients, the majority could be found different size of thyroid remnants using the three imaging methods, and only few patients(2.1%) could reach no thyroid remnant. There was no association between the volume of thyroid remnant and the outcome of RAI therapy in univariate analysis (χ₂ = 1.633, P = 0.652) and multivariate analysis (P > 0.05). In the subgroup of patients with high-risk factors, there was still no significant difference (intermediate risk subgroup: P = 0.338 vs high risk subgroup: P = 0.263).

CONCLUSION

Different sizes of thyroid remnants were left after surgery. However, in high radioiodine activity, the volume of thyroid remnants may not affect the outcome of RAI therapy even in patients with some high-risk factors, so the high radioiodine activities may resolve the the problem caused by thyroid remnants in some cases.

SIZE OF THE LARGEST METASTATIC FOCUS TO THE LYMPH NODE IS ASSOCIATED WITH INCOMPLETE RESPONSE OF PN1 PAPILLARY THYROID CARCINOMA

Objective: To evaluate the influence of the size of the metastatic focus in lymph nodes (LNs) on therapeutic response among papillary thyroid cancer (PTC) and cervical pathologically proven LN metastases (pN1). Methods: Patients with pN1 PTC who underwent total or near-total thyroidectomy, LN dissection, and postoperative radioactive iodine therapy in a university hospital between 2014 and 2016 were retrospectively reviewed. Furthermore, 554 patients were assigned to three groups according to the size of the metastatic focus in the LNs (≤0.2 cm, 0.2 to 1.0 cm, ≥1.0 cm). Structural incomplete response (SIR) was defined as structural or functional evidence of disease with any thyroglobulin level and/or anti-thyroglobulin antibodies. Results: Among the 554 patients, the proportion of patients with SIR was 2.5% (4/161) in group 1, 13.9% (37/267) in group 2, and 46.8% (59/126) in group 3 (χ² = 100.073; P<.001). The optimal cutoff value of the size of the largest metastatic focus to the LNs was 0.536 cm to predict SIR with a corresponding sensitivity of 0.82, a specificity of 0.716, and an area under the curve of 0.821 (95% confidence interval [CI], 0.777 to 0.864; P<.001). Size of the largest metastatic focus to the LNs was confirmed to be an independent predictive factor for SIR (odds ratio, 9.650; 95% CI, 4.925 to 18.909; P<.001). Conclusion: In patients with pN1 PTC, there is an association between the size of the largest metastatic focus to the LNs and incomplete response. Abbreviations: AJCC = American Joint Committee on Cancer; ATA = American Thyroid Association; BIR = biochemical incomplete response; CI = confidence interval; ER = excellent response; ETE = extranodal extension; 18F-FDG = 18F-fluorodeoxyglucose; IDR = indeterminate response; LN = lymph node; OR = odds ratio; PET/CT = positron emission tomography/computed tomography; pN1 = pathologically proven LN metastases; PTC = papillary thyroid carcinoma; RAI = radioactive iodine; ROC = receiver operating characteristic; SIR = structural incomplete response; sTg = stimulated thyroglobulin; TgAb = anti-thyroglobulin antibody; TSH = thyroid-stimulating hormone.

Risk of recurrence in patients with papillary thyroid carcinoma and minimal extrathyroidal extension not treated with radioiodine

PURPOSE

This study evaluated the recurrence rate in patients with papillary thyroid carcinoma (PTC) and minimal extrathyroidal extension (mETE) who had low thyroglobulin (Tg) after total thyroidectomy, and therefore, did not receive radioactive iodine (RAI).

METHODS

This was a prospective study including 182 patients with tumors ≤ 4 cm and mETE without aggressive histology or clinically apparent lymph node involvement (cN0pNx). After thyroidectomy, all patients had nonstimulated Tg ≤ 0.3 ng/ml, negative antithyroglobulin antibodies (TgAb), and neck ultrasonography (US) showing no anomalies. Because of these results, the patients were not submitted to RAI.

RESULTS

The time of follow-up ranged from 24 to 132 months (median 72 months). One hundred and seventy-eight patients (97.8%) continued to have nonstimulated Tg ≤ 0.3 ng/ml and negative US. Four patients (2.2%) exhibited an increase in Tg and lymph node metastases (structural recurrence). After surgery, these patients obtained nonstimulated Tg < 1 ng/ml and no apparent tumor was detected by the imaging methods.

CONCLUSION

The results suggest that patients with mETE and without other adverse features, who have low nonstimulated Tg and negative neck US after thyroidectomy, do not require ablation with RAI.