Long-term effects of radioiodine treatment on thyroid functions and ultrasonographic features in patients with toxic adenoma and toxic multinodular goitre

OBJECTIVE

This study aimed to investigate the long-term effect of radioiodine (RAI) treatment on thyroid functions and ultrasonographic changes in the thyroid gland and toxic nodules.

METHODS

Thyroid function tests and ultrasonography reports of patients diagnosed with toxic adenoma (TA) or toxic multinodular goitre (TMNG) between 2000 and 2021 were retrospectively analysed.

RESULTS

We included 100 patients whom thyroid function and ultrasonography results were obtained from our outpatient clinic before and at least 36 months post-RAI. At the end of the follow-up period, the mean thyroid volume reduction in patients with TA and TMNG was 56.6% ± 3.1% and 51.1% ± 6.7%, respectively; the mean volume decrease of all toxic nodules was 80.5% ± 1.9%. The volume of the thyroid and toxic nodules was significantly reduced up to 12 years (p < 0.01). Between 3 and 10 years after RAI therapy, the annual incidence of hypothyroidism was 2.0% and 1.5% in the TA and TMNG groups, respectively. Toxic nodules were more frequently solid and hypoechoic in post-RAI ultrasounds (p < 0.01).

CONCLUSIONS

The volume of thyroid gland and toxic nodules continuously decreases, as the risk of hypothyroidism increases up to 10 years after RAI treatment. After RAI treatment, patients should be followed up to check their thyroid functions. In post-RAI examinations, toxic nodules may show ultrasonographic features suspicious for malignancy. History taking should include previous RAI therapies and old scintigraphy scans should be evaluated to avoid unnecessary procedures and non-diagnostic biopsy results.

Postoperative Radioiodine Treatment within 9 Months from Diagnosis Significantly Reduces the Risk of Relapse in Low-Risk Differentiated Thyroid Carcinoma

Purpose

Although postoperative radioiodine (RAI) therapy has been used in patients with differentiated thyroid carcinoma (DTC) for many years, there is still lack of data defining the timing of RAI administration. A retrospective analysis was carried out to answer the question whether the time of postoperative RAI treatment demonstrated any impact on long-term outcomes, particularly in low-risk DTC.

Material

The analyzed group involved 701 DTC patients staged pT_1b-T₄N₀-N₁M₀, who underwent total thyroidectomy and postoperative RAI therapy. According to the time interval between DTC diagnosis and RAI administration, patients were allocated to one of three groups: up to 9 months (N = 150), between 9 and 24 months (N = 323), and > 24 months (N = 228). Median follow-up was 12.1 years (1.5–15.2).

Results

Based on an initial DTC advancement and postoperative stimulated thyroglobulin concentration patients were stratified as a low-, intermediate-, and high-risk group. Low-risk patients, who received RAI therapy up to 9 months, demonstrated significantly lower risk of relapse comparing to those, in whom RAI was administered between 9 and 24 months and after 24 months since DTC diagnosis: 0%, 5.5%, and 7.1%, respectively. Regarding intermediate- and high-risk groups, the differences in the timing of postoperative RAI treatment were not significant.

Conclusion

If postoperative RAI treatment is considered in low-risk DTC, any delay in RAI administration above 9 months since diagnosis may be related to poorer long-term outcomes.

Radioiodine treatment of differentiated thyroid cancer related to guidelines and scientific literature

In differentiated thyroid cancer (DTC), radioiodine is administered to eliminate residual normal thyroid tissue after thyroidectomy (ablative treatment), to treat residual microscopic disease (adjuvant treatment), and to treat macroscopic or metastatic disease. Currently, treatment of DTC with ¹³¹I is still a matter of controversy due to the absence of prospective clinical trials assessing its benefit in terms of overall survival and recurrence-free interval. The current recommendations of the experts are based on observational retrospective data and on their interpretation of the literature. Pending the results of the prospective trials that are currently underway, the use of ¹³¹I seems to be justified not only in high-risk patients, but also in intermediate-risk and low-risk patients. The guidelines of The American and British Thyroid Association, European and American Societies of Nuclear Medicine, The European Consensus Group and the latest edition of National Comprehensive Cancer Network (NCCN) were considered in drawing up this continuing education document, we also undertook a review of the related scientific literature.

The evaluation of protective and mitigating effects of vitamin C against side effects induced by radioiodine therapy

The goal of this study was to evaluate the protective and mitigative effect of vitamin C on oxidative stress in differentiated thyroid cancer (DTC) patients ablated with radioiodine. 58 DTC patients selected for radioactive iodine therapy (RAIT) with 5550 MBq ¹³¹Iodine were divided into four groups. Group 1 (control group) consisted of patients who underwent RAIT routinely. Other patients received 1500 mg vitamin C daily 2 days after (group 2), 2 days before to 2 days after (group 3) and 2 days before RAIT (group 4). Serum oxidative stress markers including malondialdehyde (MDA), glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD) were measured immediately before and 2 days after RAIT. A significant increase in MDA after RAIT was observed in all groups (p < 0.05). The concentrations of MDA were significantly higher in the control group compared to the intervention groups (p < 0.05). A significant decrease in the control group (p < 0.05) and increase in group 4 (p < 0.05) were observed in GSH level after RAIT (p < 0.05). Mean variation of GSH was significant between control group with groups 3 (p < 0.01) and 4 (p < 0.01). The results indicate that activity of SOD remained unchanged in all groups (p > 0.05). A significant increase was observed in CAT activity after RAIT in all groups (p < 0.05), which was higher in control group than intervention groups. In groups 3 (p < 0.05) and 4 (p < 0.05), this increase in CAT activity was significantly lower than the control group. RAIT causes serum oxidative stress, which can be ameliorated using vitamin C as an antioxidant. These results indicate that radioprotective effect of vitamin C is preferable to its mitigative effect.

A Functional Scoring System Based on Salivary Gland Scintigraphy for Evaluating Salivary Gland Dysfunction Secondary to 131I therapy in Patients with Differentiated Thyroid Carcinoma

INTRODUCTION

Radioiodine therapy with ¹³¹I (¹³¹I therapy) after total or near-total thyroidectomy has been established as an effective treatment for Differentiated Thyroid Carcinoma (DTC), but can induce dry mouth symptoms by salivary gland damage and impair the patients' quality of life.

AIM

To propose a functional scoring system based on Salivary Gland Scintigraphy (SGS) findings that evaluates development of salivary gland dysfunction secondary to ¹³¹I therapy in patients with DTC.

MATERIALS AND METHODS

This retrospective study evaluated the records of 279 DTC patients who underwent SGS after one or more round(s) of ¹³¹I therapy, using 370 MBqof ^99mTc-pertechnetate. The SGS results were assessed using a novel functional scoring system in the Parotid Glands (PGs) and Submandibular Glands (SMGs) according to visual evaluations based on a three-point uptake score, Washout Rate (%WR) score after lemon-juice stimulation, and functional score. The scores were compared among pre treatment, low-dose (<10 GBq), and high-dose (>10 GBq) groups and among pre treatment, symptom-positive, and symptom-negative groups. Risk factors for dry mouth were analyzed by univariate and multivariate logistic regression analyses.

RESULTS

Dry mouth symptoms developed in 15.4% of the DTC patients after ¹³¹I therapy. The three-point uptake, %WR, and functional scores in both the PG and SMG were statistically significant between low-dose and high-dose groups, and between symptom-positive and symptom-negative groups. The PG/SMG functional scores were independent risk factors for dry mouth (odds ratio, 0.03 and 0.0007 respectively).

CONCLUSION

SGS-based PG and SMG functional scores were effective biomarkers to objectively evaluate salivary gland dysfunction, with the high strength of association with dry mouth symptoms.

Radioiodine Treatment and Thyroid Hormone Suppression Therapy for Differentiated Thyroid Carcinoma: Adverse Effects Support the Trend toward Less Aggressive Treatment for Low-Risk Patients

Over the past decades, the incidence of differentiated thyroid carcinoma (DTC) has steadily increased, with especially a growing number of low-risk patients. Whereas DTC used to be treated rather aggressively, it is now acknowledged that aggressive treatment does not affect outcome for low-risk patients and that it can induce adverse effects. In this review an overview of the most clinically relevant adverse effects of radioiodine treatment and thyroid hormone suppression therapy (THST) is presented, and the trend toward less aggressive treatment for low-risk patients is outlined. Salivary gland dysfunction occurs in roughly 30% of patients, and is probably due to the concentration of radioiodine in the salivary glands by the sodium/iodide symporter. Beta radiation from radioiodine can result in sialoadenitis and eventually fibrosis and loss of salivary function. Furthermore, patients can experience bone marrow dysfunction following radioiodine treatment. Although this is in general subclinical and transient, patients that receive very high cumulative radioiodine doses may be at risk for more severe bone marrow dysfunction. THST can induce adverse cardiovascular effects in patients with DTC, such as diastolic and systolic dysfunction, and also adverse vascular and prothrombotic effects have been described. Finally, the effects of THST on bone formation and resorption are outlined; especially postmenopausal women with DTC on THST seem to be at risk of bone loss. In the past years, advances have been made in preventing low-risk patients from being overtreated. Improved biomarkers are still needed to further optimize risk stratification and personalize medicine.

Behavior and awareness of thyroid cancer patients in Korea having non-hospitalized low-dose radioiodine treatment with regard to radiation safety

PURPOSE

With the recent increase in incidence of thyroid cancer, non-hospitalized low-dose (NH-LD) radioiodine treatment (RIT) has also increased rapidly. The radioactivity limit that is allowed to be administered without hospitalization depends on individual calculation, based partly on patients' behavior. In this study, Korean patients' behavior in relation to radiation safety in NHLD RIT was surveyed.

METHODS

A total of 218 patients who underwent NH-LD RIT of 1.1 GBq (131)I in a single center were surveyed. The patients underwent RIT with a standard protocol and the survey was performed by interview when they visited subsequently for a whole-body scan. The survey questionnaire included three parts of questions: general information, behavior relating to isolation during RIT, and awareness of radiation safety.

RESULTS

After administration of radioiodine, 40% of patients who returned home used mass transportation, and another 47% went home by taxi or in car driven by another person. Isolation at home was generally sufficient. However, 7% of patients did not stay in a separate room. Among the 218 patients, 34% did not go home and chose self-isolation away from home, mostly due to concerns about radiation safety of family members. However, the places were mostly public places, including hotels, resorts, and hospitals. About half of the patients replied that access to radiation safety information was not easy and their awareness of radiation safety was not satisfactory. As a result, 45% of patients wanted hospitalized RIT.

CONCLUSIONS

In many countries, including Korea, RIT is continuously increasing. Considering the radiation safety of patients' family members or the public and the convenience of patients, the pretreatment education of patients should be enhanced. In addition, the hospitalization of patients having low-dose therapy is recommended to be seriously considered and expanded, with the expansion of dedicated treatment facilities.

Management of thyroid cancers

Thyroid cancers cover a large spectrum of disease with diametrically opposite prognosis. At one end of the spectrum we have the well differentiated cancers which carry an excellent prognosis, while at the other end there is anaplastic cancer with high mortality rates and dismal prognosis. Management of thyroid cancers still has some controversial issues due to lack of randomized controlled trials. Extent of surgery, extent of neck dissection, role of radioiodine treatment and thyroid stimulating hormone suppression are still debatable. In this review, we highlight these controversial issues and give guidelines for the management and follow up of patients with thyroid cancer.