Radioiodine-remnant ablation in low-risk differentiated thyroid cancer: pros

Advances in the selection and timing of postoperative radioiodine treatment in patients with differentiated thyroid carcinoma

Differentiated thyroid cancer (DTC) is the most common endocrine malignancy. Patients who receive systematic care typically have a better prognosis. RAI treatment plays a key role in eradicating any remaining thyroid lesions in DTC patients, hence decreasing the risk of distant metastases and cancer recurrence. As research continues to advance, RAI treatment is becoming more and more individualized. Because of the excellent prognosis for DTC patients, there is a relatively broad window for RAI treatment, making it easy to overlook when to receive RAI treatment. However, research on this issue can help patients with varying recurrence risk stratification make better decisions about when to begin RAI treatment following surgery, and physicians can schedule patients based on the severity of their disease. This will improve patient prognosis and lessen needless anxiety in addition to helping solve the problems of unjust healthcare resource distribution. In this review, we will mainly discuss the target population of RAI treatment as well as studies that examine the impact of RAI treatment timing on patient outcomes. In an effort to discourage DTC patients and physicians from selecting RAI therapy at random, we also review the possible negative effects of this treatment.

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.

Role of 131I in low-risk differentiated thyroid cancer

Differentiated thyroid cancer (DTC) is the most frequent endocrine neoplasm, with an increase in recent decades. Papillary carcinoma is the most frequent histological subtype and a large number of cases are related to tumors of small size and with little clinical repercussion, detected incidentally or as a consequence of the availability of diagnostic techniques. The "good prognosis" of the majority of cases has maintained for years the controversy in the approach to these patients, especially in two basic aspects of the therapeutic protocol: surgery and the administration of radioiodine. While in metastatic and high-risk patients, the administration of ¹³¹I therapy is widely accepted, in intermediate-low risk patients its use is highly questioned. In this paper we review the available evidence on radioiodine therapy in low-risk patients.

Randomised comparison of 1.1 GBq and 3.7 GBq radioiodine to ablate the thyroid in the treatment of low-risk thyroid cancer: a 13-year follow-up

Purpose: The optimal activity of radioiodine (I-131) administered for ablation therapy in papillary and follicular thyroid cancer after thyroidectomy remains unknown in a long-term (> 10 year) follow-up. Some, shorter follow-up studies suggest that activities 1.1 GBq and 3.7 GBq are equally effective. We evaluated the long-term outcomes after radioiodine treatment to extend current knowledge about the optimal ablative dose of I-131.Methods: One hundred and sixty consecutive adult patients (129 females, 31 males; mean age 46 ± 14 y, range 18-89 y) diagnosed with histologically confirmed differentiated thyroid cancer, were randomised in a prospective, phase III, open-label, single-centre study, to receive either 1.1 GBq or 3.7 GBq of I-131 after thyroidectomy. At randomisation, patients were stratified according to the histologically verified cervical lymph node status and were prepared for ablation using thyroid hormone withdrawal. No uptake in the whole-body scan with I-131 and serum thyroglobulin concentration less than 1 ng/mL at 4-8 months after treatment was considered successful ablation.Results: Median follow-up time was 13.0 years (mean 11.0 ± 4.8 y; range 0.3-17.1 y). Altogether 81 patients received 1.1 GBq with successful ablation in 45 (56%) patients. In the original study, thirty-six patients (44%) needed one or more extra administrations to replete the ablation. Of these, 4 (8.9%) and 5 (14%) patients relapsed during the follow-up, respectively. Of the 79 patients treated with 3.7 GBq 45 (57%) had successful ablation after one administration of radioiodine and 34 (43%) needed several treatments. Of these, 2 (4.4%) and 9 (26.5%) patients relapsed, respectively. The groups did not differ in the proportion of patients relapsing (p = .591).Conclusion: During follow-up of median 13 years, 3.7 GBq is not superior to 1.1 GBq in the radioiodine treatment after thyroidectomy in papillary and follicular thyroid cancer.

New paradigms in the treatment of low-risk thyroid cancer

INTRODUCTION

Thyroid cancer is the most common endocrine malignancy. Multiple different staging systems have been introduced and used for differentiated thyroid carcinoma (DTC).

AREAS COVERED

In this literature review we provide an overview of the standard options for management of patients with low risk differentiated thyroid cancer.

EXPERT OPINION

Surgery is considered the first and most important step in managing DTC with goal to remove all the malignant foci in order to achieve cure and increase the survival with least chance of recurrence. Many studies have been conducted to determine the best surgical approaches and how aggressive surgeries should be in order to achieve the best outcomes regarding efficacy as well as safety. Radioactive iodine (RAI) therapy has also been a part of the treatment regimen and is used for different purposes with three main goals: post-surgical ablation, adjuvant therapy and persisted/recurrent disease treatment. Radiation therapy, on the other hand, is still not recommended to be used routinely in DTC because of the conflicting data of its benefit.

Radioactive Iodine Therapy in Differentiated Thyroid Cancer: 2020 Update

OBJECTIVE. The paradigm of theranostics is based on tailoring therapy for the purpose of optimizing outcomes. This principle is being applied to radioactive iodine therapy. Consequently, thyroid cancer therapy protocols are evolving. The purpose of this article is to promote a modern approach to radioiodine therapy. CONCLUSION. This article highlights guidelines and position statements, summarizes the prognostication systems of thyroid cancer, and reviews which prescribed activities of ¹³¹I.

Salivary gland function in thyroid cancer patients with radioiodine administration history

AIM

Radioiodine (RAI) improves survival in patients with locally advanced or metastatic differentiated thyroid carcinoma (DTC). Although there has been an ongoing debate on RAI-induced salivary gland damage, published data have been inconsistent. Therefore, the purpose of our study was to compare salivary gland function in intermediate and high risk DTC patients after single or repeated RAI treatment with their age- and sex-matched RAI-naive counterparts.

METHODS

Uptake and excretion of parotid and submandibular glands were quantitatively evaluated using ^99mTc-pertechnetate salivary gland scintigraphy in 23 patients previously treated with RAI. Patients (median 9.25 GBq ¹³¹I-NaI; Q1-Q3: 5.55-16.65; range: 5.55-27.5) were divided into subgroups according to previously administered ¹³¹I-NaI activity using cut-off values 5.55 GBq and 9.25 GBq. Their salivary gland scintigraphy results were compared with RAI-naive patients using Mann-Whitney test.

RESULTS

Compared to RAI-naive patients, parotid glands pertechnetate uptake was significantly lower in those treated with > 9.25 GBq (P=0.034) and parotid glands excretion fraction was already decreased with RAI activities > 5.55 GBq (P=0.031). In submandibular glands, no statistically significant difference in either function was observed even with RAI activity > 9.25 GBq.

CONCLUSION

Our data suggest that RAI therapy using activities ≤ 5.55 GBq does not substantially decrease saliva production. Activities > 5.55 GBq may lead to significant decrease in parotid excretion, and activities > 9.25 GBq also diminish parotid uptake. Surprisingly, submandibular glands, providing majority of seromucinous saliva under basal condition, seem to be unaffected even by RAI activities above 9.25 GBq.

DIFFERENTIATED THYROID CANCER IN PEDIATRIC POPULATION (≤18 YEARS): POSTOPERATIVE TREATMENT WITH RADIOACTIVE IODINE (I-131)

The aim is to present data on the treatment and follow-up in a cohort of patients with pediatric thyroid cancer who underwent total thyroidectomy and received postoperative radioactive iodine (I-131) therapy. The study was conducted in a tertiary high-volume thyroid center, in pediatric patients with differentiated thyroid cancer who were consecutively treated during the 1965-2015 period. A total of 45 patients aged ≤18 years having undergone total thyroidectomy with or without selective neck dissection were included in the study. Decision on postoperative I-131 ablation was based on tumor characteristics, postoperative thyroglobulin level, preablative whole body scintigraphy, and/or neck ultrasound. Median age at diagnosis was 15 years. The presence of cervical lymph node metastases was significantly associated with papillary thyroid cancer, larger tumor size, involvement of two thyroid lobes, and multifocal disease. The presence of distant metastases was significantly associated with larger tumor size. None of the patients died during follow-up period, and the 5-year and 10-year overall survival rates were 100%. The 5-year and 10-year progression-free survival (PFS) rates were 87% and 73%, respectively. Male gender (p=0.046), age ≤15 years (p=0.029) and tumor size >15 mm (p=0.042) were significantly associated with inferior PFS. A significant positive trend of increase in the number of newly diagnosed patients was observed over time (p=0.011). Clinical management of pediatric thyroid cancer is challenging, especially in the light of increasing incidence in this population. Male patients younger than 15 years and with tumors of more than 15 mm in size require additional caution due to lower PFS observed.

Use of radioiodine-131 scan to measure influence of surgical discipline, practice, and volume on residual thyroid tissue after total thyroidectomy for differentiated thyroid carcinoma

BACKGROUND

Our study's purpose is to determine the influence of surgical discipline, surgeon site, and volume on remnant thyroid tissue visualized on radioactive iodine-131 (I-131) scans after total thyroidectomy and I-131 ablation in patients with well-differentiated thyroid carcinomas.

METHODS

We retrospectively reviewed all cases of patients who received I-131 therapeutic ablation and postablation radioactive I-131 scans at our center after thyroidectomy to calculate the fraction of administered dose multiplied by 1000 (UDR1000).

RESULTS

The remnant thyroid tissue (ie, the UDR1000), between academic and community surgeons was 0.471 (±0.705) and 1.190 (±2.487), respectively (P = .001). The UDR1000 between otolaryngology-head and neck surgery and general surgery was 0.654 (±1.575) and 1.043 (±1.625), respectively (P = .159). The UDR1000 partitioned by patient frequencies of <10, 10 to 19, and ≥20 patients yielded 1.255 (±2.554), 0.926 (±2.084), and 0.467 (±0.721), respectively (P = .003).

CONCLUSION

Our study found statistically significant differences in residual thyroid tissue visualized on radioactive I-131 scans based on surgeon parameters.

Clinical outcomes and associated factors of radioiodine-131 treatment in differentiated thyroid cancer with cervical lymph node metastasis

Cervical lymph node metastasis (CLNM) is common in differentiated thyroid cancer (DTC). Radioiodine-131 (¹³¹I) treatment is recommended for the removal of residual thyroid tissue following thyroidectomy. To date, the effect of ¹³¹I therapy on the outcomes of patients with DTC with CLNM is unclear. The aim of the present study was to evaluate the final outcome of patients with DTC with CLNM according to ¹³¹I administration, and to analyze the factors that may affect clinical outcomes. A total of 357 patients with DTC with CLNM were recruited and divided into three groups: Those who received 2, 3 or 4 doses of ¹³¹I therapy, respectively. Successful ablation was defined as levels of stimulated serum thyroglobulin <2 ng/ml in the absence of CLNM. The rates of successful ablation were 80.35 (229/285), 76.36 (42/55) and 70.59% (12/17) for patients who received 2, 3 and 4 doses, respectively. The patients with DTC with CLNM who were <45 years old, with tumor sizes <2 cm, solitary nodules and TNM stage I-II disease exhibited significantly higher rates of successful ablation compared with the patients who were ≥45 years old, with tumor size ≥2 cm, multiple nodules and stage III-IV disease. Multivariate analyses revealed that tumor size, number of nodules and TNM stage were independent risk factors associated with successful ablation in patients with DTC with CLNM who received 2 doses of ¹³¹I therapy. ¹³¹I administration is a useful therapy to eradicate cervical lymph node metastasis in patients with DTC, and may be preferentially indicated in patients with DTC with CLNM who are aged <45 years, with tumor sizes <2 cm, solitary nodules and lower TNM stages, in order to control and prevent recurrence and/or metastases.

Problematic clinical trials in thyroid cancer: the issue of papillary carcinoma and observational approaches

We describe the clinical ethics problem of American thyroid cancer patients being offered ‘observation’ instead of the USA standard of care with questionable informed consent. This problem arose because some American practitioners misinterpreted 1990s Japanese studies. American proponents of these studies failed to recognize major differences in ethical oversight between Japanese and US clinical research, misrepresenting these studies as justifying clinical practices for higher risk patients that were not supported by data. The current professional environment in American thyroid cancer management is sufficiently problematic that consideration should be made, for patients who have inadvertently consented to nonevidence-based treatments, to be recontacted and provided an opportunity to revisit their care plans or seek second opinions regarding an observational approach.

Radioactive Iodine Remnant Ablation: The Beta-knife Completion Thyroidectomy

The rationale and objectives for radioactive iodine (RAI) ablation remain perplexing to many. This review addresses the meaning, clinical context and the goals of “ablation”: the RAI treatment after a total thyroidectomy. This article also aims to clarify the definition of a total thyroidectomy and how a thyroid remnant can introduce a confounding factor in the postoperative management of patients with differentiated thyroid cancer. The implications of an existing thyroid remnant on RAI diagnostic imaging and serum thyroglobulin levels are discussed. This review provides a rational approach validating the utility of RAI remnant ablation regardless of the patient’s risk stratification.

Re-ablation I-131 activity does not predict treatment success in low- and intermediate-risk patients with differentiated thyroid carcinoma

The aim of this study was to evaluate the efficacy of different radioactive iodine (I-131) activities used for re-ablation, to compare various combinations of treatment activities, and to identify predictors of re-ablation failure in low- and intermediate-risk differentiated thyroid carcinoma (DTC) patients. The study included 128 consecutive low- and intermediate-risk patients with DTC with ablation failure after total thyroidectomy. Patient characteristics, T status, tumor size, lymph node involvement, postoperative remnant size on whole-body scintigraphy, serum thyroglobulin (Tg), thyroid-stimulating hormone (TSH), anti-Tg antibody (TgAb), and Tg/TSH ratio were analyzed as potential predictors of the re-ablation success. Re-ablation was successful in 113 out of 128 patients (88.3 %). Mean first I-131 activity was 2868 ± 914 MBq (77.5 ± 24.7 mCi) and mean second I-131 activity 3004 ± 699 MBq (81.2 ± 18.9 mCi). There was no association between the first, second, and cumulative activity with re-ablation treatment outcome. Treatment failure was associated with higher Tg levels prior to re-ablation (Tg2) (OR 1.16, 95 % CI 1.05-1.29, P = 0.003) and N1a status (OR 3.89, 95 % CI 1.13-13.41, P = 0.032). After excluding patients with positive-to-negative TgAb conversion, Tg2 level of 3.7 ng/mL predicted treatment failure with a sensitivity of 75.0 %, specificity of 80.5 %, and a negative predictive value of 97.1 %. Patients with positive-to-negative TgAb conversion had higher failure rates (OR 2.96, 95 % CI 0.94-9.29). Re-ablation success was high in all subgroups of patients and I-131 activity did not influence treatment outcome. Tg may serve as a good predictor of re-ablation failure. Patients with positive-to-negative TgAb conversion represent a specific group, in whom Tg level should not be used as a predictive marker of treatment outcome.

Is radioiodine administration in patients with papillary thyroid multifocal microcarcinoma unnecessary?

Radioiodine (RAI) has played a crucial role in differentiated thyroid cancer treatment for more than 60years. However, the use of RAI administration in patients with papillary thyroid microcarcinoma (even multifocal) is now being widely discussed and often not recommended. In accordance with European consensus, and contrary to the American Thyroid Association (ATA) guidelines, we recently performed RAI thyroid remnant ablation in a patient with differentiated papillary multifocal microcarcinoma. The post-therapeutic whole-body scan and SPECT/CT revealed the real and unexpected extent of disease, with metastases to upper mediastinal lymph nodes. This finding led to the patient’s upstaging from stage I to stage IVa according to the American Joint Committee on Cancer/International Union Against Cancer criteria.

Informed consent for low-risk thyroid cancer

Significant barriers to informed consent surround the clinical management of adult patients with well-differentiated thyroid cancer. The literature reveals lack of disclosure surrounding clinical equipoise; confusing and conflicting terminology; and an insufficient number of prospective trials with proper ethical oversight. We provide guidance for valid consent to treatment in this population, and propose stipulative definitions for a variety of terms used in this context. Three critical areas are addressed: surgical management, radioactive iodine management and nonvalidated practice. Sound ethical frameworks for valid consent in patients with low-risk thyroid cancer include consent to observational (or ‘active surveillance’) research protocols, consent to nonvalidated practice and consent when there are opposing standards of care due to insufficient data and disagreement among the community of experts.