Correlation between remnant thyroid gland I-131 uptake and serum thyroglobulin levels: can we rely on I-131 whole body scans?

BACKGROUND: I-131 treatment (RAI) decision relies heavily on serum thyroglobulin (Tg) levels, as higher Tg levels are assumed to be correlated with higher I-131 uptake. Tg elevation, negative iodine scintigraphy (TENIS) definition is becoming more clinically relevant as alternative treatment methods are available. This study examined the correlation between Tg levels with I-131 uptake in remnant thyroid gland to evaluate the reliability of serum Tg levels in predicting I-131 uptake. METHODS: From March 2012 to July 2019, 281 papillary thyroid cancer patients treated with 150 mCi RAI were retrospectively enrolled. Early (2nd day) and Delayed (7th day) post-RAI whole-body scan (WBS) neck counts were correlated with clinical and pathologic findings. Patients with normal neck ultrasound and undetectable level of serum Tg (< 0.2 ng/mL) and thyroglobulin antibody (TgAb) (< 10 IU/mL) were defined as ablation success within 2 years after I-131 ablation. RESULTS: Thyroid gland weight, tumor size and thyroiditis were independent factors of preoperative serum Tg levels. Serum off-Tg levels correlated with Early and Delayed WBS neck counts, and thyroiditis pathology contributed to lower neck counts in both Early and Delayed WBSs. In multivariable analysis, Delayed WBS neck count, serum off-Tg and off-TgAb were significant factors for predicting ablation success. CONCLUSION: I-131 uptake and retention in remnant thyroid gland correlates with serum off-Tg levels, thyroiditis, and ablation success in thyroid cancer patients receiving high-dose I-131 therapy. Semi-quantitative I-131 analysis with Early and Delayed WBSs provides additional information in evaluating ablation success, with the potential application for metastasis treatment response evaluation.

Antithyroglobulin Antibody as a Marker of Successful Ablation Therapy in Differentiated Thyroid Cancer.

The aim of this study was to determine the role of antithyroglobulin antibody (ATA) serum as a marker of successful I-131 ablation therapy in differentiated thyroid cancer (DTC) patients with low serum thyroglobulin (Tg). A retrospective study was conducted on 60 patients (10 males and 50 females). All patients underwent posttotal thyroidectomy and received 2.96 to 3 GBq I-131 ablation. Subjects were divided into two groups with succesful and unsuccessful I-131 ablation therapies. The data of age, gender, histopathologic type, tumor size, and metastasis were collected. Preablation serum Tg and ATA level (Tg1 and ATA1) 6-12 months after ablation (Tg2 and ATA2) were measured. The success of ablation therapy was evaluated by diagnostic whole body scan (DxWBS) 6-12 months after ablation. There were no significant differences in age, gender, type of histopathology, tumor size, and nodal metastasis between the two groups. ATA2 ≤30 kIU/L were found in 23 (62.2%) subjects with successful ablation therapy, and ATA2 >30 kIU/L in 16 (69.6%) subjects belonged to the unsuccessful group (P = 0.017). Changes between ATA1 and ATA2 levels did not differ significantly in both the groups (P = 0.062). Tg1 <10 mg/L was found in 26 (57.8%) subjects with successful therapy (P = 0.037). Multivariate analysis showed ATA2 and Tg1 as the independent factors for the success of ablation therapy (P = 0.007 and 0.015). Adjusted odds ratio of postablation ATA was 5.379 [95% confidence interval (CI) 1.590 to 18.203] and preablation Tg was 5.822 (95% CI 1.418 to 23.902). ATA levels at 6-12 months after ablation, by considering the preablation Tg levels, is a useful marker to determine successful ablation therapy in WDTC patients with low serum Tg. Changes in serum ATA levels, although not statistically significant, can provide additional information about the course of the disease.

Correlation of Consecutive Serum Thyroglobulin Levels During Hormone Withdrawal and Failure of Initial Radioiodine Ablation in Thyroid Cancer Patients.

OBJECTIVE: The aim of this study was to evaluate the value of thyroglobulin (Tg) kinetics during preparation of radioiodine ablation for prediction of initial radioiodine ablation failure in thyroid cancer patients. METHODS: Thyroid cancer patients after total thyroidectomy who underwent radioiodine ablation with 3-4 weeks of hormone withdrawal between May 2011 and January 2012 were included. Consecutive serum Tg levels 5-10 days before ablation (Tg1) and on the day of ablation (Tg2) were obtained. The difference between Tg1 and Tg2 (ΔTg), daily change rate of Tg (ΔTg/day) and Tg doubling time (Tg-DT) were calculated. Success of initial ablation was determined by the results of the follow-up ultrasonography, diagnostic radioiodine scan and stimulated Tg level after 6 to 20 months. RESULTS: A total of 143 patients were included. Failed ablation was reported in 52 patients. Tg2 higher than 5.6 ng/ml and Tg-DT shorter than 4.2 days were significantly related to a high risk of ablation failure. ΔTg and ΔTg/day did not show significant correlation with ablation failure. CONCLUSIONS: Thyroglobulin kinetics on consecutive blood sampling during hormone withdrawal may be helpful in predicting patients with higher risk of treatment failure of initial radioiodine ablation therapy in thyroid cancer patients.

Comparison of effective I-131 half-life between thyroid hormone withdrawal and recombinant human thyroid-stimulating hormone for thyroid cancer: a retrospective study.

INTRODUCTION: Preparation for postoperative radioiodine ablation for differentiated thyroid carcinoma is performed by either thyroid hormone withdrawal or recombinant human thyroid-stimulating hormone (rhTSH) administration. There is little information on the impact of the method of preparation with respect to whole-body effective I-131 half-life and its potential clinical implications in the Australian setting. METHODS: A retrospective study was performed on patients admitted for adjuvant radioiodine ablation for non-metastatic differentiated thyroid carcinoma at the Royal Adelaide Hospital over a 4½-year period from 2009. Dose rate measurements were analysed for 19 rhTSH and 31 thyroid hormone withdrawal patients. RESULTS: The mean effective I-131 half-lives were 11.51 and 13.29 h for the rhTSH and thyroid hormone withdrawal groups, respectively, with no statistically significant difference between the two groups (P = 0.761). This result differs from previously published data where withdrawal periods were typically longer, resulting in slower renal clearance and longer half-lives for withdrawal patients. CONCLUSIONS: Our study did not demonstrate a significant difference in whole-body effective half-life of I-131 between the two methods of preparation for radioiodine ablation. This suggests that putative advantages of rhTSH over withdrawal in terms of whole-body radiation dose, duration of hospital admission and quality of life may be sensitive to duration of withdrawal.

Stimulated Serum Thyroglobulin Level at the Time of First Dose of Radioactive Iodine Therapy Is the Most Predictive Factor for Therapeutic Failure in Patients With Papillary Thyroid Carcinoma.

PURPOSE: To investigate the clinical importance of serum thyroglobulin (Tg) levels just before high-dose I-131 ablation therapy (preablation Tg) for predicting therapeutic failure in patients with papillary thyroid carcinoma (PTC). METHODS: Patients with PTC (n = 132) undergoing total thyroidectomy followed by the first high-dose I-131 ablation therapy (HI-Rx) were included in this retrospective review. Just before HI-Rx, preablation Tg, anti-Tg antibody, and TSH were measured. The patients were followed up for a mean period of 7 months (range 6-23 months) by I-123 whole-body scans (f/u IWBS) and stimulated Tg (f/u Tg). Therapeutic failure was defined by positive f/u IWBS or f/u Tg >2 ng/ml. We classified patients into three groups according to the value of preablation Tg (group 1, <1 ng/ml; group 2, ≥1 and <10 ng/ml; group 3, ≥10 ng/ml) and compared clinical variables to therapeutic response. RESULTS: Therapeutic failure was noted in 39 patients (29.5 %). On univariate analysis, T stage, tumor size, and preablation Tg were the statistically significant factors that could predict therapeutic failure. After multivariate analysis, preablation Tg was the only independent predictor of therapeutic failure (P < 0.001). The therapeutic failure rate was significantly increased as the preablation Tg level increased (11.3 %, 33.3 %, and 87.5 % in groups 1, 2, and 3, respectively; P < 0.001). Individuals with preablation Tg levels ≥10 ng/ml had 25.5 times greater chance of therapeutic failure than those with levels <10 ng/ml (95 % CI = 5.43-119.60; P < 0.001). CONCLUSIONS: A high preablation Tg level is the most significant predictor of therapeutic failure at the time of first HI-Rx in patients with PTC.

Multiple Bone Metastases in a Patient with Differentiated Thyroid Cancer (DTC): Complete resolution following thyroidectomy and four ablation doses of I-131.

Multiple bone metastases from a differentiated thyroid cancer are usually incurable. We report the case of a young Omani woman who presented with 8 discrete skeletal lesions three years after a total thyroidectomy. Following four ablation doses of I-131 she has remained in clinical and biochemical remission for over five years. An extraordinary aspect of this case was the persistent refusal of her husband to use contraception either for himself or his wife. This resulted in her treatment being delayed for more than 6 years during which time the patient delivered and breastfed four additional healthy babies.

Ablation of Remnant Thyroid Tissue with I-131 in Well Differentiated Thyroid Cancer After Surgery / 대한핵의학회잡지

To evaluate the effectiveness of I-131 in ablation of residual thyroid tissue, we analyzed 350 patients with thyroid cancer who were treated with various doses of I-131 after surgery for thyroid cancer. Two hundred fifty five patients were treated with l.lGBq(30mCi) of I-131 for ablation of remnant thyroid and one hundred seventeen patients received more than 2.8GBq(75mCi) of I-131. We determined the effectiveness of ablation by following I-131 whole body scan. Absent visible uptake or minimal uptake in thyroid tissue were considered as successful ablation. Of 255 patients who received doses of 30mCi I-131 therapy, 131 patients(51%) showed successful ablation of residual thyroid tissue with 2.6+/-1.7 times of I-131 therapy. Of 117 patients who received doses of the more than 75mCi I-131, 84 patients(72%) had successful remnant thyroid ablation with 1.6+/-1.1 times of I-131 therapy. According to the extent of surgery, successful ablation rates were 78%, 62%, 54%, 33% in patients who underwent total thyroidectomy, subtotal thyroidectomy, lobectomy and isthmectomy, lobectomy or tumorectomy, respectively. This study showed that ablation of remnant thyroid after surgery with 30mCi I-131 was successful only in 50%. Therefore, in cases of patients with high risk for recurrence, we recommend high dose I-131 for ablation of remnant after total thyroidectomy.