Clinical Outcomes after Early and Delayed Radioiodine Remnant Ablation in Patients with Low-Risk Papillary Thyroid Carcinoma: Propensity Score Matching Analysis

Analysis of delayed initial radioactive iodine therapy and clinical outcomes in papillary thyroid cancer: a two-center retrospective study

BACKGROUND

It remains unclear whether the time interval between total thyroidectomy and radioactive iodine (RAI) therapy influences clinical outcomes in papillary thyroid carcinoma (PTC). This study aims to evaluate the impact of the timing to initiate RAI therapy on the response in PTC patients.

METHODS

We retrospectively included 405 patients who underwent total thyroidectomy and subsequent RAI therapy at two tertiary hospitals in southwest China. Patients were categorized into two groups based on the interval between thyroidectomy and initial RAI therapy, that is, an early group (interval ≤90 days, n = 317) and a delayed group (interval >90 days, n = 88). Responses to RAI therapy were classified as excellent, indeterminate, biochemical incomplete, or structural incomplete. Univariate and multivariate analyses were conducted to identify factors associated with a nonexcellent response.

RESULTS

Excellent responses were observed in 77.3% of the early group and 83.0% of the delayed group (P = 0.252). No significant impact of RAI therapy timing was also observed across all American Thyroid Association risk classification categories. These findings persisted when patients were analyzed separately according to RAI dose (intermediate-dose group: 3.7 GBq [n = 332]; high-activity group: ≥5.5 GBq [n = 73]), further subdivided by the timing of RAI therapy. Multivariate analysis identified lymph node dissection, RAI dose, and stimulated thyroglobulin as independent risk factors for excellent response (P < 0.05).

CONCLUSION

The timing of initial RAI therapy following surgery did not significantly affect outcomes in patients with PTC.

Ablation Rates and Long-Term Outcome Following Low-Dose Radioiodine for Differentiated Thyroid Cancer in the West of Scotland: A Retrospective Analysis

OBJECTIVE

Low-dose radioiodine is an accepted means of remnant ablation in patients with low- to intermediate-risk differentiated thyroid cancer (DTC) based on the results of several phase III trials. We evaluated the rate of ablation success and long-term recurrence outcomes in the first 3 years of implementing this practice at our institution.

METHODS

Patients who received 1.1 to 1.2 gigabecquerel (30 millicurie) were identified retrospectively from the radionuclide database, January 1, 2012, to December 31, 2014, inclusive. Successful ablation was defined as Iodine-131uptake <0.1% on diagnostic scan and Tg level <2.0 ng/mL at 6 to 8 months after treatment. Follow-up was conducted annually for 10 years and relapse rates were determined based on the available clinical, radiological, and biochemical information.

RESULTS

We identified 114 patients, 109 of whom had dual response assessment. The median age was 43 years (range, 14 to 80 years). Almost 70% had T1 or T2 tumors, with T3 and T4 tumors recorded in 27% and 2.5% of patients, respectively. Nodal staging was performed in just over 30% and involved lymph nodes were detected in 21% (N1a 8% and N1b 13%). Ablation success based on diagnostic scan alone was 94.7% (108/114), Tg alone 94.7% (108/114), and on both modalities was 90.4% (103/114).

CONCLUSION

Remnant ablation was achieved in >90%, and the corresponding clinical recurrence rate was only 1.8% despite the inclusion of patients with locally advanced disease. Low-dose radioiodine is effective and may be suitable for a proportion of patients with higher-risk DTC.

Dynamic risk assessment in patients with differentiated thyroid cancer

The current approach for patients with differentiated thyroid carcinoma should be individualized according to the risk of recurrence, and this stratification could be used to identify the risk of persistent/recurrent disease in three scenarios: preoperatively, immediately postoperatively, and during long-term follow-up. The initial risk of recurrence will tailor the management of the patient in the preoperative and immediate postoperative settings, while the dynamic risk, which considers the responses to treatment, could guide the decision-making process for remnant ablation and long-term management.This review provides a summary of the existing information regarding the dynamic risk of recurrence and recommended management for patients with differentiated thyroid cancer. The application of this approach is essential to avoid unnecessary treatments for most patients who will have a favorable prognosis. On the other hand, it allows specific therapeutic interventions for those patients at high risk of recurrence. In the future, analysis of tumor biology and prospective studies will surely improve the accuracy of recurrence risk prediction.

Patient Preparation and Radiation Protection Guidance for Adult Patients Undergoing Radioiodine Treatment for Thyroid Cancer in the UK

Radioactive iodine is a highly effective treatment for thyroid cancer and has now been used in clinical practice for more than 80 years. In general, the treatment is well tolerated. However, it can be logistically quite complex for patients due to the need to reduce iodine intake and achieve high levels of thyroid-stimulating hormone prior to treatment. Radiation protection precautions must also be taken to protect others from unnecessary radiation exposure following treatment. It has been well documented by thyroid cancer patient support groups that there is significant variation in practice across the UK. It is clear that some patients are being asked to observe unnecessarily burdensome restrictions that make it more difficult for them to tolerate the treatment. At the instigation of these support groups, a multidisciplinary group was assembled to examine the evidence and generate guidance on best practice for the preparation of patients for this treatment and the management of subsequent radiation protection precautions, with a focus on personalising the advice given to individual patients. The guidance includes advice about managing particularly challenging situations, for example treating patients who require haemodialysis. We have also worked together to produce a patient information leaflet covering these issues. We hope that the guidance document and patient information leaflet will assist centres in improving our patients' experience of receiving radioactive iodine. The patient information sheet is available as Supplementary Material to this article.

Delay of initial radioactive iodine therapy beyond 3 months has no effect on clinical responses and overall survival in patients with thyroid carcinoma: A cohort study and a meta-analysis

Background

More than a third of thyroid carcinoma (TC) patients require treatment with radioactive iodine (RAI), but the timing of initial RAI therapy after thyroidectomy remains controversial.

Methods

We included 1224 differentiated thyroid carcinoma (DTC) patients during 2015–2019, divided them into the early (≤3 months) and the delayed (>3 months) groups based on the interval between surgery and the initial RAI. Clinical outcomes were assessed within 6–8 months of treatment with RAI, including excellent response (ER), indeterminate response (IDR), biochemical incomplete (BIR) and structural incomplete response (SIR). Further transformed them into dichotomous outcomes, we therefore introduced the ordered/binary logistic regression to assess the relation of time interval and quaternary/dichotomous outcomes, respectively. Finally, we conducted a meta‐analysis for cohort study to investigate the effect of timing of RAI therapy on the prognosis of TC.

Results

Delay RAI therapy beyond 3 months reduced the IR (BIR + SIR) rate in the present cohort study (RR = 0.67, 95% CI: 0.49–91). Following meta‐analysis including 38,688 DTC patients confirmed these results (RR = 0.77, 95% CI: 0.66–0.91), further revealed the duration of treatment does not influence OS (pooled RR = 1.05, 95% CI: 0.83–1.33).

Conclusion

Delayed initial RAI therapy beyond 3 months but no later than 6 months did not impair the prognosis of TC.

Radioactive Iodine for Papillary Thyroid Carcinoma

Radioactive iodine is given after total thyroidectomy for remnant ablation or treatment of residual/metastatic disease. The decision and dose of radioactive iodine should be in a personalized and patient-specific approach, taking account the clinical-pathological features, risk stratification, patient's preference, and facilities of the institutions. We review the principles and use of radioactive iodine in differentiated thyroid cancer.