In Patients With Low- to Intermediate-Risk Thyroid Cancer, a Preablative Thyrotropin Level of 30 μIU/mL Is Not Adequate to Achieve Better Response to 131I Therapy

Clinicopathological features affecting the efficacy in 131I ablation therapy of papillary thyroid carcinoma with lymph node metastasis

Background

Lymph node metastasis is the major cause of increased recurrence and death in patients with papillary thyroid carcinoma (PTC). We evaluate the clinicopathologic factors affecting excellent response (ER) in patients with PTC with lymph node metastasis following operation and 131I ablation therapy.

Methods

A total of 423 patients with PTC with lymph node metastasis who underwent thyroidectomy and postoperative 131I ablation therapy were enrolled. The relationship between clinicopathological factors affecting ER achievement was analyzed.

Results

Multivariate analysis showed that the foci diameter (≤1 cm), unifocal, combination with Hashimoto's thyroiditis (HT), lymph node metastases rate (LR) (≤40%), no postoperative lymph node metastasis, low preablative stimulated thyroglobulin (ps-Tg) level (≤3.87 ng/mL), and the time of 131I ablation therapy (one time) were positively correlated with the ER achievement [odds ratio (OR): 1.744, 3.114, 3.920, 4.018, 2.074, 9.767, and 49.491, respectively; all p < 0.05]. The receiver operating characteristic (ROC) curves showed that the cutoff values of ps-Tg and LR were 4.625 ng/mL and 50.50%, respectively. The AUC of ROC of ps-Tg and LR for predicting ER achievement was 0.821 and 0.746, respectively. The Tg and the cumulative risk of non-ER elevated with the increase of LR, especially for the high-level ps-Tg (>4.625 ng/mL) group.

Conclusion

The foci diameter and number, combination with HT, LR, and ps-Tg level are independent factors for ER. Ps-Tg level and LR are valid predictive factors for the efficacy of 131I therapy in patients with PTC. The predictive value of the cumulative risk of non-ER can be improved by the combination of ps-Tg and LR.

Stimulating thyroglobulin to TSH ratio predict long-term efficacy of 131I therapy in patients with differentiated thyroid cancer after total thyroidectomy: a retrospective study

OBJECTIVE

This study utilized the stimulated thyroglobulin (sTg) to thyroid stimulating hormone (TSH) ratio to predict the long-term efficacy of 131I therapy in patients with moderate-to-high-risk differentiated thyroid cancer (DTC).

METHODS

This study retrospectively analyzed 960 DTC patients with a median follow-up time of 30 months (6-92 months). The median age was 44 years. All patients underwent total thyroidectomy, lymph node dissection, and at least one 131I therapy. Patients were subjected to a final efficacy evaluation according to American Thyroid Association's 2015 guidelines. Patients were grouped according to their TSH levels before the initial 131I therapy and the final efficacy evaluation, and factors influencing TSH levels and final efficacy were analyzed. Construction of nomograms using independent risk factors affecting long-term outcomes. The cut-offs of sTg and sTg/TSH ratios were calculated for different long-term outcomes. Progression-free survival (PFS) of patients was analyzed by making Kaplan-Meier survival according to the cut-offs of sTg and sTg/TSH ratio.

RESULTS

TSH (mU/L) levels were more concentrated at 60-90 in females (71.5%) and 30-60 in males (39.0%), while patients with younger age, more lymph node metastases, shorter time interval between surgery and the first 131I therapy, and lower dose of levothyroxine sodium taken prior to the first 131I therapy would have higher TSH levels (All P < 0.05).Patients who are male, have primary tumor involvement of the strap muscles, lymph node metastasis, distant metastasis, and higher sTg and sTg/TSH are more likely to have poor long-term outcomes (All P < 0.05).The cut-offs of sTg and sTg/TSH for long-term efficacy were 7.515 and 0.095. STg, sTg/TSH, tumor size, lymph node metastasis, and distant metastasis were shown to be independent risk factors for long-term efficacy. The mean PFSs were longer for patients who had sTg/TSH ≤ 0.095 and/or sTg≤7.515 ug/L.

CONCLUSIONS

For patients with moderate-to-high-risk DTC, when sTg>7.515 ug/L and/or sTg/TSH > 0.095 before the first 131I therapy, patients are more likely to have a poor long-term efficacy after full 131I therapy. This means that this group of patients may require further surgical treatment or targeted drug therapy after 131I therapy.

Sufficiency of a Single Negative Thyroglobulin Standard for Judging the Success of Ablation in Low- and Intermediate-risk Differentiated Thyroid Cancer: A Retrospective Study

BACKGROUND

We investigated how reduced successful ablation criteria may be used to evaluate radioiodine remnant ablation in patients with low- and intermediate-differentiated thyroid carcinoma (DTC).

METHODS

Overall, 254 low- and intermediate-risk patients with DTC were categorized into three groups (positive, weak, positive, and negative) on the basis of a visual study of thyroid imaging performed before postoperative iodine treatment. Semi-quantitative analysis parameters were incorporated into the positive Tc-99m pertechnetate scanning to further examine the clinical use of thyroid imaging. We investigated the value of successful judgment criteria and the influencing factors of radioiodine ablation. At the same time, the predictive value of thyroglobulin (Tg) for radioiodine treatment and the overall clinical efficacy were assessed.

RESULTS

A total of 250 (98.43%) patients were identified as having functional thyroid tissue residue on the Rx-whole-body scan, and 137 (53.94%) patients had positive Tc-99m pertechnetate scans using semi-quantitative analysis. The single Tg standard could not substitute the double standard (χ2c=22.042, p<0.001) for patients with residual thyroid weight by a semiquantitative analysis. However, the semi-quantitative analysis revealed no association between 99mTcO4-thyroid scan and ablation treatment using semi-quantitative analysis; only preablation sTg levels were related with success in the multivariate logistic regression analysis, with a cut-off value of 2.88 ng/mL. The pre-ablation stimulated Tg level was also the primary factor of satisfactory response following follow-up with an optimal cut-off of 6.506 ng/mL.

CONCLUSION

Even in low- and intermediate-risk patients with DTC, a single negative Tg standard also requires receiving some restrictions in the evaluation of ablation success and is inadequate. Conventional 99mTcO4 thyroid imaging combined with a quantitative analysis program can improve the clinical practice of single negative Tg standard.

Novel recombinant human thyroid-stimulating hormone in aiding postoperative assessment of patients with differentiated thyroid cancer-phase I/II study

PURPOSE

Thyroid hormone withdrawal (THW) inevitably induced hypothyroidism in patients with differentiated thyroid cancer (DTC), and we aimed to evaluate the safety and efficacy of a novel recombinant human thyroid-stimulating hormone (rhTSH, ZGrhTSH) as an alternative of THW in China.

METHODS

Totally, 64 DTC patients were enrolled with 24 in the dose-escalation cohort equally grouped into 0.9 mg × 1 day, 0.9 mg × 2 day, 1.8 mg × 1 day, and 1.8 mg × 2 day dosage, and 40 further enrolled into 0.9 mg × 2 day dose-expansion cohort. All patients underwent both ZGrhTSH phase and levothyroxine (L-T₄) withdrawal phase for self-comparison in terms of TSH levels, the radioactive iodine (RAI) uptake, stimulated thyroglobulin level, and the quality of life (QoL).

RESULTS

In ZGrhTSH phase, no major serious adverse events were observed, and mild symptoms of headache were observed in 6.3%, lethargy in 4.7%, and asthenia in 3.1% of the patients, and mostly resolved spontaneously within 2 days. Concordant RAI uptake was noticed in 89.1% (57/64) of the patients between ZGrhTSH and L-T₄ withdrawal phases. The concordant thyroglobulin level with a cut-off of 1 μg/L was noticed in 84.7% (50/59) of the patients without the interference of anti-thyroglobulin antibody. The QoL was far better during ZGrhTSH phase than L-T₄ withdrawal phase, with lower Billewicz (- 51.30 ± 4.70 vs. - 39.10 ± 16.61, P < 0.001) and POMS (91.70 ± 16.70 vs. 100.40 ± 22.11, P = 0.011) scores which indicate the lower the better. Serum TSH level rose from basal 0.11 ± 0.12 mU/L to a peak of 122.11 ± 42.44 mU/L 24 h after the last dose of ZGrhTSH. In L-T₄ withdrawal phase, a median of 23 days after L-T₄ withdrawal was needed, with the mean TSH level of 82.20 ± 31.37 mU/L. The half-life for ZGrhTSH clearance was about 20 h.

CONCLUSION

The ZGrhTSH held the promise to be a safe and effective modality in facilitating RAI uptake and serum thyroglobulin stimulation, with better QoL of patients with DTC compared with L-T₄ withdrawal.

Preablative Stimulated Thyroglobulin and Thyroglobulin Reduction Index as Decision-Making Markers for Second Radioactive Iodine Therapy in Patients with Structural Incomplete Response

Purpose

The aim of this study was to evaluate the value of preablative stimulated thyroglobulin (presTg) and thyroglobulin reduction index (TRI) to predict the different responses to second radioactive iodine (RAI) therapy in differentiated thyroid cancer (DTC) patients with structural incomplete response (SIR).

Patients and Methods

A single-center retrospective study analyzed the different clinical outcomes after second RAI therapy in 206 patients with SIR. PresTg1 and presTg2 were measured before first and second RAI management and TRI was the reduction index of presTg1 and presTg2. Cut-off values of presTg and TRI were obtained using receiver operating characteristic analysis. The univariate logistic regression analysis was performed to confirm these parameters as prognostic factors to predict different responses to second RAI therapy.

Results

Only ATA risk stratification, the post-therapy whole-body scanning (Rx-WBS) findings, presTg1, presTg2, TRI, were different in patients with SIR. After second RAI therapy, 28.2% (58/206) of patients with SIR initially were reclassified as excellent response (ER). PresTg1 <6.6 ng/mL, presTg2 <1.2ng/mL, and TRI >74.2% were excellent indications to predict ER from non-ER after second RAI treatment. PresTg1 >14.9 ng/mL, presTg2 >1.8ng/mL and TRI <66.5% were well markers to predict poor outcome (SIR). High risk and distant metastases could still be considered as risk factors.

Conclusion

DTC patients with SIR could benefit through second RAI treatment. PresTg before each RAI therapy and TRI could be considered as effective decision-making markers for second RAI therapy and as predictive indications for clinical outcomes.

A pre-ablative thyroid-stimulating hormone with 30-70 mIU/L achieves better response to initial radioiodine remnant ablation in differentiated thyroid carcinoma patients

Our aim was to clarify the optimum pre-ablative thyroid-stimulating hormone (TSH) level for initial radioiodine remnant ablation (RRA) in patients with differentiated thyroid carcinoma (DTC). From December 2015 to May 2019, 689 patients undergone RRA at Nuclear Medicine Department, Second Hospital of Shandong University were included in the study. Patients were categorized by their pre-ablative TSH level grouping of < 30, 30–70 and ≥ 70 mIU/L. Response to RRA were evaluated as complete response (including excellent and indeterminate response) and incomplete response (including biochemical and structural incomplete response) after a follow-up of 6–8 months. Multivariable binary logistic regression model was used to explore the optimum pre-ablative TSH level range and independent factors associated with response to RRA. Rates of complete response to RRA were 63.04%, 74.59% and 66.41% in TSH level groups of < 30, 30–70 and ≥ 70 mIU/L, separately. With multivariate analysis, the study found that pre-ablative TSH levels, gender and lymph node dissection were independent predictors of response to RRA. TSH between 30 and 70 mIU/L had a higher rate of complete response compared with TSH < 30 mIU/L, OR 0.451 (95% CI 0.215–0.958, P = 0.036). A pre-ablative TSH level of 30–70 mIU/L was appropriate for patients with DTC to achieve a better response to RRA.

The Influences of TSH Stimulation Level, Stimulated Tg Level and Tg/TSH Ratio on the Therapeutic Effect of 131I Treatment in DTC Patients

PURPOSE

To study the influences of pre-ablation TSH stimulation level, sTg and sTg/TSH ratio on the therapeutic effect of the first ¹³¹I treatment in DTCs.

METHODS

According to the thyroid stimulating hormone (TSH) levels (mU/l), all the 479 differentiated thyroid cancer (DTC) patients were divided into two groups: TSH < 30 and TSH ≥ 30. The TSH ≥ 30 group was divided into three subgroups: 30 ≤ TSH < 60, 60 ≤ TSH < 90 and TSH ≥ 90. The clinical features and the therapeutic effects of the first ¹³¹I treatment were analyzed. The cutoffs of stimulated thyroglobulin (sTg) and sTg/TSH ratio were calculated to predict the therapeutic effect of ¹³¹I treatment.

RESULTS

Among the three subgroups, the TSH ≥ 90 subgroup was younger and less likely to be associated with cervical lymph node metastasis (LNM). The postoperative levothyroxine (L-T₄) dose in the 60 ≤ TSH < 90 subgroup was the lowest. Between the two groups, patients in the TSH < 30 group had higher postoperative L-T₄ dose and longer thyroid hormone withdrawal (THW) time. The excellent response rates six months after the first ¹³¹I treatment among the three subgroups and between the two groups were not of statistical significance. The distribution of different TSH stimulation levels among each response group was similar. The cutoffs for the better therapeutic effect of the first ¹³¹I treatment in sTg and sTg/TSH were < 9.51 ng/ml and < 0.11, respectively. Both univariate and multivariate logistic regressions showed that cervical LNM, distant metastasis, higher sTg and higher sTg/TSH ratio predicted poorer therapeutic effect.

CONCLUSIONS

There was no significant influence of TSH stimulation levels before the first ¹³¹I treatment on the therapeutic effect of DTC. The sTg/TSH ratio can be considered as another predictor of ¹³¹I therapeutic effect.

Evaluation of SNA001, a Novel Recombinant Human Thyroid Stimulating Hormone Injection, in Patients With Differentiated Thyroid Carcinoma

SNA001 is a novel recombinant human thyroid stimulating hormone (rhTSH). rhTSH has long been approved in several countries to facilitate monitoring and ablation of thyroid carcinoma without hypothyroidism caused by thyroid hormone withdrawal (THW). To assess the safety, tolerance, pharmacokinetic and pharmacodynamic properties of SNA001, the two-period (SNA001 period and THW period), dose-ascending study in well-differentiated thyroid cancer (DTC) patients was designed. Three doses (0.45 mg, 0.9 mg, and 1.35 mg) of SNA001 were intramuscularly injected, twice in the SNA001 period to stimulate iodine-131 uptake and thyroglobulin (Tg) release. 24 h after the last dose of SNA001, iodine-131 (111-185 MBq) was administrated, followed by whole-body scan (WBS) 48 h later. THW period began just after SNA001 washout and lasted for about 3-6 weeks. When TSH level was above 30 mU/L, iodine-131 (111-185 MBq) was administrated, followed by a WBS and Tg detection 48 h later. Twenty-four DTC patients after thyroidectomy were enrolled; mean peak concentrations of SNA001 in 0.45, 0.9, and 1.35 mg groups were 18.5, 26.7, and 37.0 ng/ml (about 244.7, 354.2, and 489.6 mU/L) respectively, within 28-32 h after first dose of SNA001. SNA001 was metabolized in a dose-dependent manner. The results of WBS and Tg release in the SNA001 period were compared with those in the THW period. Compared to Tg level in baseline, the Tg levels in SNA001 and THW periods were increased, with 78% of subjects showing higher Tg levels in the THW period. 100% of the patients had concordant qualitative results of the scans within two periods in three groups. Symptoms of hypothyroidism were relieved in the SNA001 period compared with THW period, though there was no significant difference in most of the scale scores. There were no serious adverse events related to SNA001; the most common adverse events were gastrointestinal symptoms of mild and transient nature. Thus, SNA001 promises to be a safe and effective method to stimulate iodine-131 uptake and Tg secretion during monitoring and ablation for DTC without the disadvantages of incidental hypothyroidism.

Efficacy and Affecting Factors of 131I Thyroid Remnant Ablation After Surgical Treatment of Differentiated Thyroid Carcinoma

Purpose: Radioiodine (¹³¹I) thyroid remnant ablation is an important treatment of differentiated thyroid carcinoma (DTC) and various factors affecting its efficacy have been reported but not well defined. The aim of our study was to evaluate the efficacy and the affecting factors of ¹³¹I ablation after total or near-total thyroidectomy in a relative large DTC cohort. Methods: 261 DTC patients with negative thyroglobulin antibody received 100-200 mCi ¹³¹I for thyroid remnant ablation after total or near-total thyroidectomy between January 2012 and October 2015 in our hospital. The efficacy and affecting factors of ¹³¹I ablation therapy were retrospectively investigated. Results: The success rate of the first ¹³¹I thyroid remnant ablation was 65.90%. Univariate analysis demonstrated that larger tumor size, higher level of pre-ablation stimulated thyroglobulin (sTg), intermediate to high risk stratification for recurrence, and lymph node and distant metastases were associated with a lower success rate of the first ¹³¹I ablation (all p < 0.05). Multivariate logistic regression analysis showed that tumor size, pre-ablation sTg, and lymph node and distant metastases were independent factors affecting the efficacy of the first ¹³¹I ablation. Areas under receiver operating characteristic curves for sTg, sTg/TSH ratio, and tumor size to predict unsuccessful ablation were 0.831, 0.824, and 0.648, respectively. The threshold values were 4.595 ng/ml, 0.046 mg/IU, and 1.350 cm, respectively. The sensitivities were 95.51, 96.63, and 73.03% and the specificities were 64.54, 61.63, and 49.41%, respectively. The excellent response (ER) ratio of the successful group was significantly higher than that of the unsuccessful group. Conclusions: The efficacy of the first ¹³¹I thyroid remnant ablation after surgical treatment of DTC is well demonstrated, and tumor size, pre-ablation sTg, lymph node, and distant metastases are independent factors affecting its efficacy.

30mCi radioactive iodine achieving comparative excellent response in intermediate/high-risk nonmetastatic papillary thyroid cancer: a propensity score matching study

OBJECTIVE

To determine the efficacy of low-dose radioactive iodine (RAI) therapy (30 mCi, 1110 MBq) in Chinese patients with intermediate- to high-risk papillary thyroid cancer (PTC) without distant metastasis.

DESIGN AND METHODS

This large retrospective study included Chinese patients with PTC that tested negative for thyroglobulin antibodies. Patients were categorized into low-dose (30 mCi, 1110 MBq) and high-dose (>100 mCi, 3700 MBq) RAI groups. Ablation rate and long-term response were compared between groups using propensity score matching (PSM) to minimize bias and confounding.

RESULTS

In total, we included 446 patients. No significant difference in ablation success rate was found between groups (P = 0.305) before or after PSM (N = 162; P = 0.200). Excellent response (ER) rate was not significant between groups before (P = 0.917) or after PSM (P = 0.798). Efficacy of low-dose RAI was similar to that of high-dose RAI in N0- (P = 1.000), N1a- (P = 0.981), and N1b-stage (P = 0.903) patients. Low- and high-dose RAI groups achieved similar ER rates in pre-ablative stimulated thyroglobulin level (≤1 ng/mL, P = 1.000; 1 < ps-Tg ≤ 5 ng/mL, P = 0.444; 5 < ps-Tg ≤ 10 ng/mL, P = 0.665; >10 ng/mL, P = 1.000) and BRAF^V600E-positive (P = 0.324) subgroups.

CONCLUSIONS

Efficacy of low-dose RAI therapy was similar to that of high-dose for ablation and achieving ER in Chinese nonmetastatic intermediate- to high-risk PTC patients. High-dose RAI could not rectify ablation failure or non-ER rates in PTC patients with BRAF^V600E, lymph node metastases, or unfavorable thyroglobulin levels.

THYROGLOBULIN AS A TUMOR MARKER IN DIFFERENTIATED THYROID CANCER - CLINICAL CONSIDERATIONS

SUMMARY – Initial treatment of the majority of patients with differentiated thyroid cancer (DTC) includes total thyroidectomy. Postoperative ablation therapy with radioactive iodine (I-131) is indicated in all high-risk patients, however, there is disagreement regarding its use in low- and intermediate-risk patients. Over the last few decades, thyroglobulin (Tg) has been established as the primary biochemical tumor marker for patients with DTC. Thyroglobulin can be measured during thyroid hormone therapy or after thyroid-stimulating hormone (TSH) stimulation, through thyroid hormone withdrawal or the use of human recombinant TSH. In many studies, the cut-off value for adequate Tg stimulation is a TSH value ≥30 mIU/L. However, there is an emerging body of evidence suggesting that this long-established standard should be re-evaluated, bringing this threshold into question. Recently, a risk stratification system of response to initial therapy (with four categories) has been introduced and Tg measurement is one of the main components. The relationship between the Tg/TSH ratio and the outcome of radioiodine ablation has also been studied, as well as clinical significance of serum thyroglobulin doubling-time. The postoperative serum Tg value is an important prognostic factor that is used to guide clinical management, and it is the most valuable tool in long term follow-up of patients with DTC.

Could short thyroid hormone withdrawal be an effective strategy for radioiodine remnant ablation in differentiated thyroid cancer patients?

PURPOSE

Current guidelines recommend thyroid hormone withdrawal (THW) of 3-4 weeks before radioiodine remnant ablation (RRA) of differentiated thyroid carcinoma (DTC). We aimed to evaluate (1) the reliability of a shorter THW (i.e., 14 days) to achieve adequate TSH levels (i.e., 30 mU/l), (2) the association between length of THW and response to therapy, and (3) the potential association between pre-ablation TSH levels and patients' outcome.

METHODS

After thyroidectomy, all patients started LT4 therapy, which was subsequently discontinued in order to perform RRA. Patients were broken down into two groups according to the length of THW: group A, 2 weeks of THW, and group B, 3-4 weeks of THW. We used clinical, biochemical, and imaging data to evaluate patients' outcome. By means of univariate and multivariate analysis, including main DTC prognostic factors, we assessed the impact of THW length and TSH levels on patients' outcome.

RESULTS

We evaluated 222 patients, 85 of whom were treated with RRA after a THW period of 2 weeks (group A). All other 137 patients underwent RRA after 3-4 weeks THW (group B). At the time of RRA all patients presented TSH levels ≥30 mU/l. After a median follow-up time of 3.4 years, we found 183 patients (82%) with excellent response to treatment and 39 patients (18%) showing incomplete response. Kaplan-Meier response to therapy curves showed that ablation-Tg, tumor size, and lymph node status were significantly associated with prognosis; no associations were found between THW length, TSH levels, and prognosis. Multivariate Cox model showed that only ablation-Tg was significantly associated with treatment response.

CONCLUSIONS

Prior to RRA, a short 2-week THW is an effective method to stimulate TSH levels. No difference in terms of incomplete response to treatment was observed between DTC patients prepared for RRA with a short THW and those with the long THW.

Quantitative thyroglobulin response to radioactive iodine treatment in predicting radioactive iodine-refractory thyroid cancer with pulmonary metastasis

OBJECTIVE

Current diagnosis of radioactive iodine (RAI)-refractory (RAIR) differentiated thyroid cancer (DTC) is based on the imaging technique, which is of a high cost. Serum thyroglobulin (Tg) is a sensitive and easily obtained biomarker. Hence, we aimed to assess the predicting value of quantitative response of Tg in earlier identifying the RAIR-DTC with pulmonary metastasis.

PATIENTS AND METHODS

Pulmonary metastatic DTC patients who underwent total or near-total thyroidectomy and at least two times of RAI therapy were included in this study. The pre-ablative stimulated Tg at the first and second RAI therapy were defined as pstim-Tg1 and pstim-Tg2, while the suppressed Tg before and after the second RAI therapy were designated sup-Tg1 and sup-Tg2. The predicted value of pstim-Tg2/Tg1 and sup-Tg2/Tg1 ratio were detected using the receiver operating characteristic (ROC) curve and logistic regression analyses.

RESULTS

Totally 115 patients were involved in this study. ROC curves showed a cut-off value of 0.544 for pstim-Tg2/ pstim-Tg1 in detecting RAIR, with a sensitivity of 0.9 and specificity of 0.477, and an area under the curve (AUC) of 0.744. Similarly, the cut-off of sup-Tg2/ sup-Tg1 was 0.972, with a sensitivity of 0.733 and specificity of 0.935, and AUC of 0.898. Univariate analysis illustrated that age, tumor size, pstim-Tg2/Tg1, sup-Tg2/ sup-Tg1 and BRAFV600E mutation were eligible to predict RAIR. While from multivariate analysis, only age, pstim-Tg2/Tg1, sup-Tg2/ sup-Tg1 and BRAFV600E mutation were verified to be the independent predictive factors.

CONCLUSION

The quantitative Tg response was encouraging in identifying RAIR-DTC with pulmonary metastasis. Age, BRAFV600E mutation and Tg response were independent predictors in predicting RAIR-DTC.

Higher preablative serum thyroid-stimulating hormone level predicts radioiodine ablation effectiveness in patients with differentiated thyroid carcinoma

INTRODUCTION

Radioiodine ablation of remnant thyroid tissue is an important adjuvant therapy of differentiated thyroid carcinoma (DTC) after thyroidectomy. Elevated serum thyroid-stimulating hormone (TSH) level is necessary for successful ablation. The optimum level of serum TSH level necessary for successful radioiodine ablation of well-DTC is, however, yet to be defined. We aimed to determine whether higher serum TSH level will result in a better rate of complete ablation of well-DTC using iodine-131 (I) following initial thyroidectomy.

PATIENTS AND METHODS

A total of 109 patients with differentiated thyroid cancer were divided into four treatment groups on the basis of serum TSH levels. They were followed up from 6 to 12 months after treatment with stimulated serum thyroglobulin level and a diagnostic whole-body scan with radioactive iodine I to determine early response.

RESULTS

Sixty-four patients had papillary thyroid carcinoma, whereas 45 patients had follicular carcinoma. An excellent response was observed in 66.7% of patients with TSH level more than 90 μIU/ml, 72.2% in the group with TSH level of 60-89 μIU/ml, 48.5% when TSH was 30-59 μIU/ml and 26.7% when TSH was less than 30 μIU/ml (P=0.002).

CONCLUSION

Higher preablative serum TSH predicts a better rate of ablation in patients with differentiated thyroid cancer treated with I after thyroidectomy.