Stimulated Serum Thyroglobulin Levels versus Unstimulated Serum Thyroglobulin in the Follow-up of Patients with Papillary Thyroid Carcinoma

Incidence of Persistence and Recurrence of Differentiated Thyroid Cancer in Post-surgical Cases From a Tertiary Care Hospital in Dubai, United Arab Emirates

Background Despite the excellent prognosis of differentiated thyroid carcinoma, recurrence remains a major concern. However, the persistence of thyroid cancer post-thyroidectomy is not uncommon. We aimed to characterise patients who underwent re-operative surgery for differentiated thyroid carcinoma and analyse the percentage of re-operations that truly were for "recurrent" disease versus the management of persistent disease. Methods We conducted a retrospective review of the hospital database, analysing patients who visited the nuclear medicine department at Mediclinic City Hospital, a tertiary care hospital in Dubai, United Arab Emirates, between 2015 and 2022. The study included patients with differentiated thyroid carcinoma who underwent re-operations after total thyroidectomy. Recurrence was defined as the development of disease after a patient had undetectable thyroglobulin and negative radiological scans within one year of the first surgery. Cases were categorised as "recurrent", "persistent", or "unable to classify" in the event of missing data. Results Out of 836 patients diagnosed with differentiated thyroid carcinoma who visited the nuclear medicine department, 71 underwent re-operations. The mean age of these patients was 44.4 years (CI 41.7-47.0), of whom 78.9% were females. Almost half (46.5%) underwent re-operations within the first year, and 98.6% were diagnosed with papillary thyroid carcinoma. We were able to classify 63.4% of cases (n=45) as persistent disease, while 24 cases were categorised as "unable to classify". Only two cases met the criteria for recurrent disease. Conclusion The majority of cases previously classified as "recurrent" in differentiated thyroid carcinoma were found to be a persistent disease, possibly indicating inadequate therapy. Further research may be required to explore the reasons behind this eye-opening rate of disease persistence. This highlights an area for improvement in the management and future outcomes of differentiated thyroid carcinoma patients.

Basal or stimulated thyroglobulin in evaluating response to treatment in papillary thyroid carcinoma? A retrospective cohort study

OBJECTIVE

It is not clear whether response to initial treatment in papillary thyroid carcinoma (PTC) patients is best evaluated by measuring thyroglobulin (Tg) in the presence of levothyroxine (BTg) or when stimulated by elevated TSH (STg). The aim of this study was to evaluate whether response to therapy 1 year after initial treatment changes with the use of STg in relation to BTg in PTC patients treated with total thyroidectomy (TT) and radioiodine (131I), and, if observed, to assess which response is better associated with clinical course.

SUBJECTS AND METHODS

This is a retrospective study of 148 PTC patients submitted to TT and 131I. We analyzed the response to therapy (excellent, biochemical incomplete, or indeterminate) at 1 year after initial treatment, using BTg or STg, and compared which method was better associated with "excellent response at final evaluation."

RESULTS

Twenty-eight patients (20.4%) presented change in response to therapy, with 17 of these (60.7%) presenting a worse response. Response using STg was 1.6 times better associated with proposed outcome [odds ratio (OR) = 4.61; confidence interval 95% (IC95%): 2.13-9.98] than with BTg (OR = 2.84; IC95%: 1.33-6.06).

CONCLUSION

Response to therapy at 1 year using STg was altered in approximately 20% of cases and therefore proved to be a better predictor of excellent response in the last evaluation.

Comparison of Prognostic Value Between Stimulated and Nonstimulated Thyroglobulins in Differentiated Thyroid Cancer: A Retrospective Study

Purpose

The growing incidence of differentiated thyroid cancer (DTC) demands dependable prognostic factors to guide follow-up and treatment plans. This study investigated the prognostic value of response to therapy (RTT) assessment using TSH stimulated-thyroglobulin (sti-Tg) and nonstimulated-thyroglobulin (nonsti-Tg) and evaluates whether RTT using nonsti-Tg (nonstiRTT) can replace RTT using sti-Tg (stiRTT) in clinical practice to improve patients' quality of life during assessment.

Methods

We enrolled 419 DTC patients who underwent total thyroidectomy, radioactive iodine (RAI) therapy, and Tg assessment. Patients with structural incomplete responses were excluded. Initial RTT assessments based on the 2015 American Thyroid Association guidelines (excellent response; ER, indeterminate response, biochemical incomplete response) were performed 6-24 months after RAI therapy. The second RTT assessments were performed 6-24 months after the first assessment. Statistical analysis for recurrence-free survival (RFS) was done with the log-rank test for stiRTT and nonstiRTT.

Results

Although initial stiRTT and nonstiRTT were significant predictors for RFS (p < 0.0001), stiRTT provided better RFS prediction than nonstiRTT. The RFS analysis of the second RTT assessment demonstrated statistical significance only for stiRTT (p < 0.0001). In 116 patients classified as ER on initial stiRTT, there was no RFS difference between patients classified as ER on either second stiRTT or nonstiRTT.

Conclusion

The prognostic power of stiRTT surpasses that of nonstiRTT in both the initial and second RTT assessment. Nevertheless, among patients classified as ER on initial stiRTT, a second stiRTT may not be required for those classified as ER on the second nonstiRTT.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13139-023-00811-8.

Radiation exposure to allied health personnel handling blood specimens from patients receiving radioactive iodine-131 and recombinant human TSH (thyrogen®) stimulation

With increasing use of recombinant human TSH (rhTSH) stimulation protocol in radioactive iodine-131 treatment of thyroidectomised differentiated thyroid carcinoma (DTC), there is increasing concern regarding radiation safety during collection and processing of radioactive blood samples. Our study aims to quantify this radiation exposure in the context of current radiation guidelines to provide a practical safety framework. We analysed 45 patients prospectively referred to a tertiary centre in Singapore, who had histologically proven DTC, and who were thyroidectomised and planned for I-131 with rhTSH stimulation. Each patient received rhTSH for two consecutive days, with I-131 administered 24 h after, and a stimulated Thyroglobulin blood sample collected and processed 72 h after the last rhTSH dose. We measured radiation exposures with dosimeters. Based on the average and maximum exposure rates calculated, we extrapolated and derived the number of radioactive blood samples that could be safely collected and processed. Mean hand and body radiation exposures during venepuncture and blood processing were generally significantly higher than background radiation. Based on average exposure rates, the permissible number of blood samples that can be collected and processed is 9.09 × 10³per year (24 per day) and 8.70 × 10⁴per year (238 per day), respectively. This is the first study to date to extrapolate permissible thresholds that can serve as a practical guideline to the number of radioactive blood samples which can be safely collected and processed, following radioactive iodine therapy, within the limits of current radiation guidelines. Once validated, generalisations to other radioactive therapies may be considered.

Undetectable thyroglobulin makes 123I whole-body scan and stimulated thyroglobulin obsolete in follow-up care of differentiated thyroid cancer: a retrospective study

Background

Differentiated thyroid cancer (DTC) is a common malignancy with increasing incidence. Follow-up care for DTC includes thyroglobulin (Tg) measurement and ultrasound (US) of the neck, combined with ¹³¹I remnant ablation when indicated. Diagnostic precision has evolved with the introduction of the new high-sensitive Tg-assays (sensitivity ≤0.1 ng/mL). The aim of the study was to determine the prognostic utility of high-sensitive Tg and the need for other diagnostic tests in DTC.

Methods

This was a retrospective, observational study. Patients with pathologically confirmed DTC, treated with total thyroidectomy and ¹³¹I remnant ablation, who had their complete follow-up care in our institution were selected (October 2013–December 2018). Subjects with possible thyroglobulin autoantibody interference were excluded. Statistical analysis was performed using the IBM SPSS® Statistics 24 software package.

Results

Forty patients were eligible for analysis. A total of 24 out of the 40 patients (60%) had an undetectable high-sensitive Tg 6 months after total thyroidectomy. None of these patients had a stimulated Tg above 1 ng/mL, or remnant on the ¹²³I Whole-Body Scan (WBS) after 1 year of follow-up. Ultrasound of the neck, performed between 6 and 12 months postoperative, was negative in 21 out of the 24 patients.

Conclusions

This study shows that an undetectable high-sensitive Tg can change the management of patients with DTC and decrease the use and need of stimulated Tg and ¹²³I WBS.

Examination of Malignant Findings of Thyroid Nodules Using Thyroid Ultrasonography

Background

It is important to distinguish benign thyroid nodules from malignant thyroid nodules. Hence, this study aimed to determine the characteristics of patients with thyroid cancer using thyroid ultrasonography.

Methods

We retrospectively examined the ultrasonographic findings of 327 patients with 457 thyroid nodules (age: 59.9 ± 14.3 years; sex, n (%): female 242 (74.0%)) at a single center from 2014 to 2016. Ultrasonography was used to determine the nodule size, shape, border, internal echogenicity, presence of coarse calcifications and microcalcifications within the nodule, internal blood flow and whether the nodule was solid or contained cystic structures. Thyroid fine needle aspiration cytology (FNAC) was performed in all patients. The ultrasonographic findings were compared between patients with benign nodules and those with papillary thyroid carcinoma (PTC). Furthermore, in the analysis of anti-thyroglobulin (Tg) antibody-negative patients with single nodules, values of serum Tg/nodule volume were calculated and compared between patients with benign nodules and those with PTC.

Results

There were 298 (65.2%) benign nodules, 33 (7.2%) PTCs and 126 (27.6%) others (104 follicular neoplasms, 19 masses of undetermined significance and three other malignant tumors). The nodules diagnosed as PTC had significantly lower internal echogenicity (P < 0.01), more microcalcifications (P < 0.01) and comprised more nodules rich in blood flow (P < 0.05) than benign nodules. Solid nodules were found significantly more in the PTC group (P < 0.01). The serum Tg/nodule volume ratio was significantly higher in the PTC group (P < 0.05).

Conclusions

Findings suggestive of PTC were found from images obtained using thyroid ultrasonography. In the diagnosis of PTC, the frequency of FNAC examinations should be reduced as this method is costly and invasive.

Can the basal serum thyroglobulin level be used to predict the recombinant human TSH-stimulated thyroglobulin level in differentiated patients with thyroid cancer?

This study investigated the correlation between basal thyroglobulin (Tg) and recombinant human thyroid-stimulating hormone (rhTSH)-stimulated Tg in differentiated patients with thyroid cancer, and sought to determine whether the basal Tg level predicts the rhTSH-stimulated Tg level.We retrospectively enrolled 177 patients with papillary thyroid cancer (mean age = 44 years; 50 males, 127 females) who received rhTSH before radioiodine therapy (RIT). Serum Tg levels were measured 7 days before the 1st rhTSH injection (basal Tg) and on the days of RIT (rhTSH-stimulated Tg). Patients were divided into 3 groups according to rhTSH-stimulated Tg cut-off levels of 2, 5, and 10 ng/mL. The correlation between basal Tg and rhTSH-stimulated Tg levels was assessed, and whether basal Tg was useful in predicting the rhTSH-stimulated Tg level was determined.A significant positive correlation was observed between basal and rhTSH-stimulated Tg levels (|rho| = 0.48, P < .0001). The basal Tg level had significant diagnostic ability in predicting an rhTSH-stimulated Tg level of 2 ng/mL or higher, and the optimal basal Tg level for this prediction was 0.3 ng/mL (AUC = 0.77, P < .0001). A basal Tg level of 0.5 ng/mL was optimal for predicting rhTSH-stimulated Tg levels of 5 ng/mL or higher (AUC = 0.81, P < .0001), and of 10 ng/mL or higher (AUC = 0.82, P = .0171).The basal Tg level was significantly correlated with the rhTSH-stimulated Tg level. If the basal Tg level is >0.3 or 0.5 ng/mL, then the rhTSH-stimulated Tg level can be expected to be sufficiently high to necessitate clinical examination.