Post-surgical ablation of thyroid remnants with high-dose (131)I in patients with differentiated thyroid carcinoma

Can shear wave elastography determine remnant thyroid tissue in the early postoperative period in patients with differentiated thyroid carcinoma?

PURPOSE

This study aims to investigate the usability of ultrasonography (US) and shear wave elastography (SWE) in detecting remnant thyroid tissue (RTT) within the first three postoperative months in patients who underwent total thyroidectomy (TT) for differentiated thyroid cancer (DTC) and who were scheduled for radioiodine (RAI) ablation therapy.

METHODS

Sixty-nine patients who underwent a TT operation due to DTC were included in the study. The participant's thyroid surgical bed was first evaluated by thyroid scintigraphy and then by greyscale US and SWE to investigate RTT. The participants were divided into two groups, those with and those without RTT. SWE quantitative data were compared between the two groups. Receiver operating characteristic (ROC) curve analysis was performed to determine the best cut-off values for stiffness and velocity in distinguishing RTT.

RESULTS

A total of 149 regions were analysed in 69 participants (43 females, 26 males). The average time elapsed after the operation was 65.2 ± 24.1 days. RTT was determined by scintigraphy and US-SWE in 38 (55%) patients. The stiffness and velocity values were significantly higher in the group with RTT than in the group without RTT. To distinguish RTT from the thyroid bed, the best cut-off values for stiffness and velocity were 15.7 kPa and 2.12 m/s, respectively.

CONCLUSIONS

US with SWE can detect RTT in the early postoperative period in patients who have undergone TT due to DTC and who are scheduled for RAI treatment. The use of US and SWE will be particularly beneficial in patients with RTT but who have false-negative Tg levels and RTT that is not I-131 avid.

Whole-remnant and maximum-voxel SPECT/CT dosimetry in 131 I-NaI treatments of differentiated thyroid cancer

PURPOSE

To investigate the possible differences between SPECT/CT based whole-remnant and maximum-voxel dosimetry in patients receiving radio-iodine ablation treatment of differentiated thyroid cancer (DTC).

METHODS

Eighteen DTC patients were administered 1.11 GBq of 131 I-NaI after near-total thyroidectomy and rhTSH stimulation. Two patients had two remnants, so in total dosimetry was performed for 20 sites. Three SPECT/CT scans were performed for each patient at 1, 2, and 3-7 days after administration. The activity, the remnant mass, and the maximum-voxel activity were determined from these images and from a recovery-coefficient curve derived from experimental phantom measurements. The cumulated activity was estimated using trapezoidal-exponential integration. Finally, the absorbed dose was calculated using S-values for unit-density spheres in whole-remnant dosimetry and S-values for voxels in maximum-voxel dosimetry.

RESULTS

The mean absorbed dose obtained from whole-remnant dosimetry was 40 Gy (range 2-176 Gy) and from maximum-voxel dosimetry 34 Gy (range 2-145 Gy). For any given patient, the activity concentrations for each of the three time-points were approximately the same for the two methods. The effective half-lives varied (R = 0.865), mainly due to discrepancies in estimation of the longer effective half-lives. On average, absorbed doses obtained from whole-remnant dosimetry were 1.2 ± 0.2 (1 SD) higher than for maximum-voxel dosimetry, mainly due to differences in theS-values. The method-related differences were however small in comparison to the wide range of absorbed doses obtained in patients.

CONCLUSIONS

Simple and consistent procedures for SPECT/CT based whole-volume and maximum-voxel dosimetry have been described, both based on experimentally determined recovery coefficients. Generally the results from the two approaches are consistent, although there is a small, systematic difference in the absorbed dose due to differences in the S-values, and some variability due to differences in the estimated effective half-lives, especially when the effective half-life is long. Irrespective of the method used, the patient absorbed doses obtained span over two orders of magnitude.

Thyroid Remnant Estimation by Diagnostic Dose (131)I Scintigraphy or (99m)TcO4(-) Scintigraphy after Thyroidectomy: A Comparison with Therapeutic Dose (131)I Imaging

In this clinical study, we have compared routine diagnostic dose ¹³¹I scan and ^99mTcO₄⁻ thyroid scintigraphy with therapeutic dose ¹³¹I imaging for accurate thyroid remnant estimation after total thyroidectomy. We conducted a retrospective review of the patients undergoing total thyroidectomy for differentiated thyroid carcinoma (DTC) and subsequently receiving radioactive iodine (RAI) treatment to ablate remnant thyroid tissue. All patients had therapeutic dose RAI whole body scan, which was compared with that of diagnostic dose RAI, ^99mTcO₄⁻ thyroid scan, and ultrasound examination. We concluded that therapeutic dose RAI scan reveals some extent thyroid remnant in all DTC patients following total thyroidectomy. Diagnostic RAI scan is much superior to ultrasound and ^99mTcO₄⁻ thyroid scan for the postoperative estimation of thyroid remnant. Ultrasound and ^99mTcO₄⁻ thyroid scan provide little information for thyroid remnant estimation and, therefore, would not replace diagnostic RAI scan.

Serum Thyroglobulin Measured With a Second-Generation Assay in Patients Undergoing Total Thyroidectomy Without Radioiodine Remnant Ablation: A Prospective Study

BACKGROUND

Follow-up consisting of the measurement of nonstimulated serum thyroglobulin (Tg) combined with neck ultrasonography is recommended for patients with papillary thyroid carcinoma without indication for radioiodine ablation. There is no recommendation of thyrotropin suppression during this follow-up. New-generation Tg assays have been increasingly used, but few studies involve patients submitted only to thyroidectomy and they have several limitations. The objective of this prospective study was to define expected concentrations of nonstimulated Tg measured with a second-generation assay after total thyroidectomy in the absence of tumor.

METHODS

Serum Tg was measured using a second-generation assay in 69 patients without tumor and serum thyrotropin between 0.5 and 2 mIU/L, 3, 6, 12, and 24 months after total thyroidectomy. All patients had undetectable anti-Tg antibodies.

RESULTS

Serum Tg was undetectable in 44.4%, 57%, 62.5%, and 62.1% of the patients 3, 6, 12, and 24 months after thyroidectomy, respectively, and was ≤0.5 ng/mL in 60.3%, 80%, 90.6%, and 90.9% of patients. All patients had a Tg≤2 ng/mL 6 months after thyroidectomy, and 97% had a Tg≤1 ng/mL 24 months after surgery. There was no case of Tg conversion from undetectable to detectable and none of the patients presented an increase in Tg.

CONCLUSIONS

An important decline in serum Tg occurred between 3 and 6 months after total thyroidectomy. One year after surgery, Tg was undetectable in approximately 60% of the patients and was ≤2 ng/mL in all of them.

Thyroid nodules and differentiated thyroid cancer: update on the Brazilian consensus

Thyroid nodules are frequent findings, especially when sensitive imaging methods are used. Although thyroid cancer is relatively rare, its incidence is increasing, particularly in terms of small tumors, which have an uncertain clinical relevance. Most patients with differentiated thyroid cancer exhibit satisfactory clinical outcomes when treatment is appropriate, and their mortality rate is similar to that of the overall population. However, relapse occurs in a considerable fraction of these patients, and some patients stop responding to conventional treatment and eventually die from their disease. Therefore, the challenge is how to identify the individuals who require more aggressive disease management while sparing the majority of patients from unnecessary treatments and procedures. We have updated the Brazilian Consensus that was published in 2007, emphasizing the diagnostic and therapeutic advances that the participants, representing several Brazilian university centers, consider most relevant in clinical practice. The formulation of the present guidelines was based on the participants' experience and a review of the relevant literature.

Thyroid remnant ablation in patients with papillary cancer: a comparison of low, moderate, and high activities of radioiodine

OBJECTIVE

The consensus about optimal activities of I-131 for thyroid remnant ablation has not yet been achieved. The aim of this study was to compare ablation rates obtained with different I-131 activities.

PATIENTS AND METHODS

The study included 466 patients divided into four groups according to I-131 activities given after total thyroidectomy for papillary thyroid cancer: group A [168 patients who received 888 MBq (24 mCi)], group B [125 patients who received 1480 MBq (40 mCi)], group C [65 patients who received 1850 MBq (50 mCi)], and group D [108 patients who received 4440 MBq (120 mCi)]. Ablation outcome was assessed by whole-body scan in hypothyroid state 6-9 months after ablation and finally 18-21 months after the treatment.

RESULTS

The rate of successful ablation was similar in the group of patients who received 24 and 40 mCi (75 and 71.2%, respectively). The higher rate of ablation was achieved in the groups treated with 50 and 120 mCi of radioiodine (87.69 and 90.74%, respectively). The ablation rates at the first follow-up examinations (59.5, 67.2, 73.9, 80.6%) were lower than at second control study (75.0, 71.2, 87.7, 90.7%) in all groups. Time required for thyroid remnant ablation seems to be >or=18 months.

CONCLUSION

Our study indicates that activity of 50 mCi seems to be optimal to achieve a successful ablation rate (approximately 90%). Low I-131 activities are acceptable for lower risk patients because of satisfactory ablation rate (>70%), lower expense, and minimal radiation burden to patients as well as lower radiation exposure to clinical staff. The ablative use of high activities seems neither justified nor optimized.

Predictive Value of the Preablation Serum Thyroglobulin Level After Thyroidectomy Is Combined With Postablation 131I Whole Body Scintigraphy for Successful Ablation in Patients With Differentiated Thyroid Carcinoma

OBJECTIVES

To investigate the clinical importance of the combined use of serum thyroglobulin (Tg) levels measured just before ablation (ablation-Tg) and postablation 131I whole body scintigraphy (WBS) patterns for predicting ablation success in patients with differentiated thyroid carcinoma who received total thyroidectomy and 131I ablation therapy.

METHODS

We retrospectively studied the early clinical outcomes for 81 differentiated thyroid carcinoma patients treated with total thyroidectomy and high-dose 131I ablation therapy between June 2001 and July 2004.

RESULTS

Ablation success was achieved in 42 (97.7%) of the 43 patients with uptake in the thyroid bed only and ablation-Tg levels less than 10 ng/mL, whereas successful ablation was achieved in 9 (75.0%) of the 12 patients with uptake in the thyroid bed only and ablation-Tg levels equal to or greater than 10 ng/mL (P = 0.029). Among 15 patients with uptake including a lymph node and ablation-Tg levels less than 10 ng/mL, 14 patients (93.3%) showed ablation success, whereas successful ablation was achieved in only 2 (18.2%) of the 11 patients with uptake including a lymph node and ablation-Tg levels equal to or greater than 10 ng/mL (P < 0.001).

CONCLUSIONS

These data indicate that the combined use of serum Tg levels measured just before ablation and the 131I WBS patterns after ablation may be an early predictor of ablation success in patients with differentiated thyroid carcinoma who received total thyroidectomy and high-dose 131I ablation therapy.

Changing Concepts in the Management of Differentiated Thyroid Cancer

The management of patients with differentiated thyroid cancer has changed significantly over the last few decades. Mortality has decreased as the result of earlier detection, refined surgical approaches, subsequent radioiodine ablation, and the development of more sensitive methods for detecting and monitoring disease recurrence. The latter has been facilitated by serum thyroglobulin measurements, the use of recombinant human thyrotropin, and the use of 18F-deoxyglucose/positron emission tomography in selected instances where radioiodine imaging fails to locate known or suspected recurrent or metastatic disease.

Valor da varredura com iodo antes da terapia ablativa em pacientes com carcinoma de tireóide

OBJETIVO: Avaliar a relevância clínica da varredura pré-dose ablativa em pacientes com carcinoma diferenciado de tireóide. MATERIAIS E MÉTODOS: Analisamos a varredura com 131I e a tireoglobulina (Tg) sérica em hipotireoidismo antes da primeira terapia ablativa em 100 pacientes submetidos a tireoidectomia total, considerando a varredura clinicamente importante quando revelou metástases ressecáveis ou que foram tratadas com doses maiores que a inicialmente proposta (100 mCi de 131I), além dos casos sem captação e com Tg < 5 ng/ml, que não receberam radioiodoterapia. RESULTADOS: A varredura revelou captação correspondente a metástases linfonodais em dez pacientes (10%), metástases distantes em cinco (5%), apenas em leito tireoidiano em 76 (76%) e foi negativa em nove (9%), sendo clinicamente relevante (indicando cirurgia, aumento da dose ou dispensando a radioiodoterapia) em 18% dos pacientes. Nos pacientes com Tg > 10 ng/ml a varredura influenciou a conduta em 41% dos casos pela presença de metástases, e naqueles com Tg < 10 ng/ml em apenas 10%, na maioria por não receberem radioiodo. CONCLUSÃO: A varredura pré-dose ablativa fornece informacões clinicamente importantes (presença de metástases) em muitos pacientes com Tg > 10 ng/ml, sendo indicada nesta condição.

Management of 131I therapy for thyroid cancer: cumulative dose from in-patients, discharge planning and personnel requirements

AIM

To provide a comprehensive overview with regard to the hospitalization/discharge planning and nursing staff requirements for the management of patients treated with radioiodine for differentiated thyroid carcinoma.

METHODS

A statistical analysis of the fast clearance phase of 131I was performed in 265 hospitalized patients treated after total thyroidectomy with fixed doses ranging from 2590 to 9250 MBq.

RESULTS

Two hundred and twenty-five cases were post-surgical ablation treatments and 40 cases were follow-up treatments. The 131I clearance was studied during hospitalization of 2-4 days. No clearance differences were found between the two groups. The median value of the biological half-time (T1/2bio) was 0.65 days, with a variability range of 0.30-2.03 days. A statistical model for the distribution of T(1/2bio) was reported. Some patients on maintenance haemodialysis were also studied, with T(1/2bio) values ranging from 1.6 to 2.6 days. The weekly cumulative dose to personnel from external exposure, corresponding to the 95th percentile, ranged from 0.1 mSv per GBq of administered activity (mSv x GBq(-1)) with a totally ambulant patient to 5.4 mSv . GBq with a totally helpless patient. With patients on maintenance haemodialysis, these values could increase from 1.2 to 1.7 times. The cumulative dose to close relatives was also estimated. The hospitalization times associated with 75% and 95% probabilities of patient discharge were calculated by varying the residual activity limit from 100 to 800 MBq. Finally, using the median T(1/2bio), personnel requirements were evaluated. With totally ambulant and semi-ambulant patients, about 0.5 and 1.0 personnel units per GBq of weekly administered activity were needed so as not to exceed an annual planning dose of 6 mSv per year. The treatment of patients with higher degrees of dependency was impractical.

CONCLUSIONS

On the basis of statistical analysis, a better organization of in-patient treatment may be obtained, as well as more accurate preliminary evaluations of the cumulative doses to nursing staff and attending personnel, for the management of patients treated with radioiodine for differentiated thyroid carcinoma.

5mCi pretreatment scanning does not cause stunning when the ablative dose is administered within 72 hours

OBJECTIVE: To determine the stunning effect of a tracer dose of 5mCi iodine-131. PATIENTS AND METHODS: We retrospectively analyzed 145 patients who received the first ablative treatment at our service. Patients were divided according to disease status determined upon post-treatment scanning (101 patients with thyroid remnants and 44 with pulmonary metastases) and whole-body scanning before ablation (performed on 69 individuals). All patients with thyroid remnants were treated with an ablative dose of 100mCi and those with metastases received 200mCi. RESULTS: In patients with remnants only (n= 41) or metastases (n= 28) submitted to diagnostic scanning, uptake was found to be apparently increased in most patientscases (71 and 73%, respectively) 7 days after therapy, while reduced uptake (visual) was not observed in any patient. The efficacy of ablation was similar in the groups submitted or not to diagnostic scanning: 71 and 80% in patients without metastases (p= 0.28), respectively, and 43 and 50% in those with pulmonary involvement (p= 0.64). CONCLUSION: The present results indicate that diagnostic scanning using a 5mCi iodine-131 dose does not interfere with uptake of the ablative dose or with treatment efficacy when ablation is performed within 72h.

Outcome of ablation of thyroid remnants with 100 mCi (3.7 GBq) iodine-131 in patients with thyroid cancer

A retrospective study was conducted on 186 patients with differentiated thyroid cancer without metastases who received an ablative dose of 100 mCi (3.7 GBq) iodine-131 after total thyroidectomy. Six months to one year after ablation, 155/186 patients (83%) had a negative scan. Diagnostic scanning with 5 mCi (185 MBq) performed 72 h or 3 months before ablation did not interfere with treatment success compared to patients not submitted to pre-therapy scanning. Pre-ablation cervical uptake values < 2% were associated with a higher ablation efficacy (94%), from 2 to 5% showed 80% success and values > 5%, 60% (p < 0.05). There were no significant differences between the responsive and no responsive groups in terms of age, sex, histological type or size of the primary tumor. 11% of the patients with low stimulated Tg (< 2 ng/ml) presented discrete thyroid bed uptake on follow-up diagnostic scan (< 0.5%) without definitive residual disease and 89% had negative uptake on scan. The patients with Tg > 2 ng/ml presented thyroid bed (10/12) or ectopic (2/12) uptake on follow-up diagnostic scan. An ablative dose of 100 mCi shows a high rate of efficacy, especially when cervical uptake is < 2%; no difference was noted between patients assessed by scan within 72 h or 3 months before treatment and those not scanned; follow-up diagnostic scan can be avoided in low risk patients with stimulated Tg < 2 ng/ml.

Pre-ablative Diagnostic Whole-body Scan Following Total Thyroidectomy for Well-differentiated Thyroid Cancer: Is It Necessary?

OBJECTIVE

This study reviewed the incidence of positive pre-ablative diagnostic scan after total thyroidectomy and the efficacy of the current ablative dose. The predictive factors for outcome using a standard ablative dose and postoperative complications of total thyroidectomy were also examined.

METHODS

This was a retrospective review of patients referred for radioiodine ablation after total thyroidectomy between September 1997 and September 2001.

RESULTS

Forty patients were included in this study, of whom 95% had a positive scan after total thyroidectomy. Of the 30 patients who underwent standard 80-mCi radioiodine ablation, 21 (70%) had successful single ablation while the remaining nine patients needed a higher ablative dose. There were no significant differences between patients who had successful ablation with the standard dose and those who did not in terms of tumour size, patient age, lymph node status and extra-thyroidal extension. Fifteen percent suffered from permanent hypoparathyroidism requiring calcium supplementation. Three patients had documented recurrent laryngeal nerve paralysis.

CONCLUSION

Bypassing the pre-ablative diagnostic scan is feasible. The present ablation dose of 80 mCi of radioiodine is effective. The relatively high postoperative morbidity after difficult total thyroidectomy suggests less aggressive excision and postoperative radioiodine ablation of the remnant tissue.

Prognostic significance of successful ablation with radioiodine of differentiated thyroid cancer patients

OBJECTIVES

Currently, little is known about the prognostic significance of achieving successful ablation with the first dosage of I-131 in patients with differentiated thyroid cancer. This study aimed to assess the following: (i) whether successful or unsuccessful ablation at post-ablation follow-up has prognostic consequences; (ii) possible factors predicting success of ablation in a patient.

METHODS

In order to do this, we retrospectively studied 180 patients with a median follow-up of 55 months. Ablation was considered to be successful if 1 year after the initial dosage of I-131 patients fulfilled all of the following criteria: not dead from thyroid cancer, no additional therapy needed for any kind for thyroid cancer within the first year, undetectable thyroglobulin (Tg) levels under TSH stimulation, and negative I-131 scintigraphy. Tg levels at the time of ablation (P < 0.001), lymph node metastasis (P = 0.04) and distant metastasis (P < 0.001) have a significant influence on the success of ablation. P values were calculated by Mann-Whitney U test and Chi-square test, respectively.

RESULTS

Patients with successful ablation had a better prognosis than those with unsuccessful ablation: disease-free survival was 87% versus 49% after 10 years; additionally, thyroid-cancer related survival was 93% versus 78%.

CONCLUSION

We conclude that the extent of the remaining normal or neoplastic thyroid tissue influences the outcome of ablation, and that successful ablation leads to a better prognosis. It seems that it is very important to achieve complete ablation as soon as possible in order to ensure the best possible prognosis for a patient.

Efficacy of low and high 131I doses for thyroid remnant ablation in patients with differentiated thyroid carcinoma based on post-operative cervical uptake

OBJECTIVE

The aim of this study was to determine the efficacy of low (1110 MBq (30 mCi)) and high (3700 MBq (100 mCi)) 131I doses on the ablation of post-surgical remnants in patients with thyroid cancer based on the measurement of post-operative cervical uptake.

METHODS

The study was conducted on 155 patients without metastases after thyroidectomy who received a 1110 or 3700 MBq ablative dose and who were assessed by pre-therapy cervical uptake. The patients were divided into six groups according to the uptake result and the dose received. Successful therapy was defined as a negative scan 6 months to 1 year after ablation.

RESULTS

Ablative therapy was successful in 90% of patients with uptake <2% who received the 1110 MBq dose (n=30) and in 92.5% of patients who received the 3700 MBq dose (n=40), P=0.95. In the group with uptakes ranging from 2% to 5%, successful therapy was observed in 65% of patients receiving 1110 MBq (n=20) and in 86.6% of patients receiving 3700 MBq (n=30), P=0.14. In patients with uptake >5%, a 46.6% success rate was obtained for the 1110 MBq dose (n=15), while efficacy was 70% in patients receiving 3700 MBq (n=20), P=0.16.

CONCLUSION

This study demonstrated the efficacy of low doses in patients with lower remnants after surgery (uptake <2%), the inverse correlation between uptake and ablation efficacy with low and high doses, and the usefulness of the measurement of cervical uptake for the definition of the ablative 131I dose.

Decreased uptake after fractionated ablative doses of iodine-131

PURPOSE

In an attempt to obviate the necessity for hospitalisation, the ablative dose of 131I in the treatment of thyroid cancer is divided into two or three fractions at weekly intervals in some hospitals with no special bed for 131I treatment. Thyroid stunning has been observed in patients receiving a 131I dose between 74 and 370 MBq (2-10 mCi). However, the influence of 131I uptake after administration of a higher dose, such as 1,110-1,850 MBq of 131I, has never been reported. In this study, we evaluated the degree of reduction in 131I uptake after patients received 1,480 MBq of 131I and evaluated the clinical value of fractionated ablative doses of 131I.

METHODS

Thirty-five patients with functional thyroid cancer received a total of 4,440 MBq (120 mCi) of 131I which was divided into three fractions administered at weekly intervals. In all patients two 131I whole-body scans were performed. The first scan was performed directly prior to the second dose of 131I (7 days after the first administration of 131I), and the second scan was performed 7 days after the second administration of 131I and directly prior to the third administration. Regions of interest including the neck and lungs were drawn to calculate the uptake of 131I in the thyroid remnant and possible cervical lymph node and lung metastases.

RESULTS

The mean uptake of 131I was 2.73% 7 days after the first administration, and decreased significantly to 0.26% 7 days after the second administration. The mean decrease was as high as 80.7%. The decrease in 131I uptake was significant in all patients except the two with lung metastases. In the two patients with lung metastases, no definite evidence of decreased uptake was noted; the uptake of 131I in the lung metastases even increased on the second 131I image in one of these patients. After administration of 1,480 MBq of 131I, the decreased uptake was significant in all neck lesions but not in lung metastases.

CONCLUSION

The use of fractionated ablative doses of 131I is not to be recommended in patients without lung metastases. However, the influence of fractionated ablative doses of 131I in patients with lung metastases is worthy of further study.

Sonography in the diagnosis of cervical recurrence in patients with differentiated thyroid carcinoma

OBJECTIVE

To determine the sensitivity of thyroglobulin (Tg), iodine scanning, and sonography in the diagnosis of cervical recurrence of thyroid cancer.

METHODS

This prospective study assessed 81 patients with cervical metastases or extrathyroid invasion at first appearance who underwent clinical examination, scanning, measurement of Tg after thyroxine withdrawal, and sonography about 8 months after thyroidectomy followed by radioiodine treatment. Only patients without distant metastases and without anti-Tg antibodies were included.

RESULTS

Fifty patients showed persistence of the disease in the cervical region, with only 16% of them having had a suspicion on clinical examination, 33 with Tg levels of 2 ng/mL or greater (66% sensitivity), and 29 with positive scan findings (58% sensitivity). A combination of the 2 methods detected disease in 40 (80%) of 50 patients but failed to show 20% of cases that were identified by sonography and confirmed by fine-needle aspiration. Sonography had sensitivity of 96%. Specificity values for Tg, iodine scanning, and sonography were 80.6%, 90.3%, and 87%, respectively.

CONCLUSIONS

Classic follow-up methods may not detect cervical disease in some patients with differentiated thyroid carcinoma, and sonography is necessary even in patients apparently free of the disease.

Diagnostic value of serum thyroglobulin measurements in the follow-up of differentiated thyroid carcinoma, a structured meta-analysis

OBJECTIVE

To investigate to what extent thyroid remnant ablation and withdrawal from thyroxine are required to achieve sufficient accuracy of serum thyroglobulin (Tg) measurements as an indicator of tumour recurrence in the follow-up of patients with differentiated thyroid carcinoma.

DESIGN AND METHODS

We conducted a meta-analysis of the literature from 1975 to 2003 on serum Tg measurements in the follow-up of differentiated thyroid carcinoma. In a computer-based search, we initially found 915 articles that were finally narrowed down to 120. These 120 papers were subjected to strict in/and exclusion criteria, leaving 46 articles (totalling 9094 patients). Data from these articles were extracted in a structured fashion and were grouped according to initial therapy, TSH status, Tg assay method and definition of a 'gold standard'. Original 2 x 2 tables were pooled by summary receiver operating characteristic curve analysis (sROCa), best estimates of sensitivity and specificity being obtained by the combination of sROCa and Mantel-Haenszel odds ratios.

RESULTS

Despite considerable differences between series in laboratory and clinical methodology, we consistently found higher specificity for Tg measurements after thyroid remnant ablation than after surgery alone. Highest pooled sensitivity 0.961 +/- 0.013 (SE) was found for immunometric assay (IMA) after thyroid remnant ablation and thyroid hormone withdrawal, at a specificity of 0.947 +/- 0.007. Pooled sensitivity decreased significantly if ablated patients were tested while on thyroid hormone (0.778 +/- 0.023, at a specificity of 0.977 +/- 0.005). Significantly decreased pooled specificity was found in patients who did not undergo remnant ablation (sensitivity 0.972 +/- 0.023, at a specificity of 0.759 +/- 0.028). If recombinant human TSH (rhTSH) stimulation was used as a substitute for thyroxine withdrawal, sensitivity remained high (0.925 +/- 0.018) while specificity decreased to 0.880 +/- 0.013. In all analyses, specificity of Tg would decrease when unspecified activity in the thyroid region at scintigraphy was considered benign, whereas sensitivity decreased when such activity was considered malignant.

CONCLUSION

This study confirms that the best accuracy of Tg-guided follow-up in patients treated for differentiated thyroid carcinoma is obtained if treatment includes remnant ablation, and Tg testing is performed while off thyroxine.

Correlation Between Cervical Uptake and Results of Postsurgical Radioiodine Ablation in Patients With Thyroid Carcinoma

OBJECTIVE

The objective of this study was to determine the relationship between cervical uptake after thyroidectomy and the success of treatment of cervical remnants with high-dose radioiodine (100 mCi).

METHODS

Cervical uptake was retrospectively analyzed after total thyroidectomy and before treatment with radioactive iodine in 142 patients seen at our service who received 100 mCi iodine-131 and whose posttreatment scan only showed cervical uptake without distant metastases. The patients were divided into 5 groups according to the uptake result obtained before ablative therapy.

RESULTS

Successful treatment, defined as stimulated thyroglobulin levels <5 ng/mL and a clean scan or only discrete cervical uptake (0.5%) 6 months to 1 year after surgery, was obtained as follows: patients with uptake <1% (n = 48) showed 95.8% treatment efficacy, those with uptake of 1-2% (n = 32) 94% efficacy, and those with uptake of 2-5% (n = 30) reached 83% success, whereas patients with uptake of 5-10% (n = 20) presented 70% efficacy, and treatment was successful in only 50% of patients with uptake >10% (n = 12).

CONCLUSIONS

Postoperative measurement of cervical I-131 uptake could be a reasonable predictor of the success of the remnant ablation, and perhaps a guide in deciding the ablative dose of I-131, based on the inverse correlation between the uptake and ablation efficacy.

Differentiated thyroid cancer: radioiodine following lobectomy — a clinical feasibility study

The surgical management of differentiated thyroid cancer remains controversial. Total thyroidectomy has been associated with higher rates of post-operative morbidity than more conservative surgery, but radioiodine ablation of residual thyroid tissue is considered to be particularly difficult after lobectomy. The purpose of this retrospective study was to assess the feasibility of 131I ablation after lobectomy, compared with total thyroidectomy, in patients who had undergone surgery for differentiated thyroid carcinoma. A retrospective analysis was performed of 225 post-surgical thyroid cancer patients treated with 3500 MBq 131I for the ablation of thyroid remnants. One hundred and sixty-five patients (73%) had previously undergone total thyroidectomy, whilst 60 patients (27%) had been treated by lobectomy. All patients underwent diagnostic scintigraphy, with 40 MBq 131I, 2 days prior to ablative therapy and at 3 months post-ablation. The median pre-ablative 131I neck uptake values were 3.3% and 20.1% in patients treated by total thyroidectomy and lobectomy, respectively (P < 0.001). Pre-ablation neck uptake correlated strongly with the whole-body 131I burden 2 days after 131I therapy (P < 0.001), and the biological half-life of the radioiodine was markedly longer after lobectomy than after total thyroidectomy. Ninety-eight per cent of patients treated by total thyroidectomy were successfully ablated by one 131I treatment, compared with 90% after lobectomy (P < 0.05). There were no significant differences in 131I neck uptake or serum thyroglobulin levels between the two patient groups at 3 months post-ablation. These data show that high rates of thyroid ablation can be achieved with a single fixed dose of 131I after thyroid lobectomy. The use of this surgical procedure may result in a longer period of patient isolation than that required after total thyroidectomy. However, the clear correlation between pre-ablation neck uptake and 131I burden at 2 days post-therapy enables effective treatment scheduling, so making lobectomy followed by 131I ablation a practical option for the management of differentiated thyroid cancer.

The Impact of Clinical Guidelines on Surgical Management in Patients with Thyroid Cancer

AIMS

Thyroid cancer is an uncommon but highly curable disease if treated optimally. The aim of this study was to determine whether clinical guidelines introduced locally at the beginning of 1999 were associated with better surgical outcome, using radioiodine uptake as a surrogate measure of completeness of thyroidectomy.

MATERIALS AND METHODS

We reviewed the medical records of all patients with thyroid cancer referred to a cancer centre (n=176) 3 years before and 3 years after the introduction of guidelines. The uptake of radioiodine in the thyroid bed after thyroidectomy and before radioiodine ablation was used to assess the completeness of primary surgical treatment.

RESULTS

The number of new cases referred to our centre increased from 80 in the 1996-1998 period to 94 during 1999-2001. This was largely because of an excess of papillary thyroid cancers. Documentation in the medical records of the pathological primary tumour size improved from 47.5% to 80.8% following the introduction of guidelines. A significant reduction in radioiodine uptake in the thyroid bed was observed following the introduction of guidelines (5.03% +/- 6.82 (SD) vs 2.75% +/- 5.10 (SD); P=0.005). Linear regression analysis of clinical variables indicated that the year of surgery was the only significant factor influencing radioiodine uptake in the thyroid bed (P=0.014). Twelve hospitals within the Northern Cancer Network carried out thyroid surgery for thyroid cancer in the pre-guideline era compared with seven hospitals in the post-guideline era. Surgeons who were members of the regional multidisciplinary thyroid cancer team operated on 35% of cases in the 1996-1998 period and 56.4% in the 1999-2001 period (P<0.01).

CONCLUSIONS

The introduction of clinical guidelines in 1999 was associated with a reduction in the size of thyroid remnant after primary surgical treatment. This was accompanied by fewer hospitals undertaking thyroid surgery and more patients being operated on by surgeons who were members of the thyroid cancer multidisciplinary team.

Influence of diagnostic and therapeutic doses on thyroid remnant ablation rates

Radioiodine ablation of thyroid tissue after subtotal thyroidectomy has been shown to decrease recurrence in certain subsets of patients with well-differentiated thyroid cancer. In a substantial percentage of cases (20-30%), initial ablation of the thyroid remnant fails, necessitating a second treatment. The factors associated with ablation failure are not fully understood. In particular, it is not certain whether the use of doses higher than 3.70 GBq would result in any additional benefit, or whether there is a 'stunning' effect of the diagnostic dose of 131I on the subsequent ablation rate. A retrospective analysis was performed of all patients (n=389) with well-differentiated thyroid cancer treated at our institution between 1992 and 2001. Remnant ablation success was determined by a whole-body radioiodine scan. The following factors, thought to be associated with thyroid remnant ablation, were studied by logistic regression analysis: age, gender, tumour histology, stage, pre-therapy neck uptake of 131I, diagnostic dose, ablation dose, time between diagnostic and therapeutic dose (T1), time between therapeutic administration and the first follow-up whole-body scan (T2) and the thyroid-stimulating hormone (TSH) level measured at the time of therapy. Follow-up whole-body scans were available in 214 patients. We found no association with age, gender, histology, TSH level, neck uptake, diagnostic dose and successful ablation. The therapeutic dose was the only variable found to be associated with success (odds ratio, 1.96 per 1.85 GBq increment; 95% confidence interval, 1.11-3.46). Our results confirm the presence of a significant percentage of ablation failures (24.4%) despite the use of high ablative doses (3.70-7.40 GBq). Higher therapeutic doses are associated with higher rates of successful ablation, even when administered to patients with more advanced stages. Using our protocol, higher diagnostic doses were not associated with higher rates of ablation failure.

Ablation of thyroid residues with 30 mCi (131)I: a comparison in thyroid cancer patients prepared with recombinant human TSH or thyroid hormone withdrawal

The aim of the study was to assess whether stimulation by recombinant human TSH (rhTSH) may be used in patients with differentiated thyroid carcinoma for postsurgical ablation of thyroid remnants using a 30-mCi standard dose of (131)I during thyroid hormone therapy. The rate of ablation was prospectively compared in three groups of patients consecutively assigned to one of three treatment arms: in the first arm, patients (n = 50) were treated while hypothyroid (HYPO); in the second arm, patients (n = 42) were treated while HYPO and stimulated in addition with rhTSH (HYPO + rhTSH); in the third arm, patients (n = 70) were treated while euthyroid (EU) on thyroid hormone therapy and stimulated with rhTSH (EU + rhTSH). The outcome of thyroid ablation was assessed by conventional HYPO (131)I scan performed in HYPO state 6-10 months after ablation. Basal serum TSH was elevated in the HYPO and HYPO + rhTSH groups. In the EU + rhTSH group, basal serum TSH was 1.3 +/- 2.5 micro U/ml (range, <0.005-11.9 micro U/ml). After rhTSH, serum TSH significantly increased in the HYPO + rhTSH group and the EU + rhTSH group. Basal 24-h radioiodine thyroid bed uptake was 5.8 +/- 5.7% (range, 0.2-21%) and 5.4 +/- 5.7% (range, 0.2-26%) in the HYPO and HYPO + rhTSH groups, respectively. In the HYPO + rhTSH group, mean 24-h thyroid bed uptake rose to 9.4 +/- 9.5% (range, 0.2-46%) after rhTSH (P < 0.0001). The 24-h uptake after rhTSH in the EU + rhTSH group was 2.5 +/- 4.3% (range, 0.1-32%), significantly lower (P < 0.0001) than that found in the HYPO and HYPO + rhTSH groups. The rate of successful ablation was similar in the HYPO and HYPO + rhTSH groups (84% and 78.5%, respectively). A significantly lower rate of ablation (54%) was achieved in the EU + rhTSH group. Mean initial dose rate (the radiation dose delivered during the first hour after treatment) was significantly lower in the EU + rhTSH group (10.7 +/- 12.6 Gy/h) compared with the HYPO + rhTSH group (48.5 +/- 43 Gy/h) and the HYPO group (27.1 +/- 42.5 Gy/h). In conclusion, our study indicates that by using stimulation with rhTSH, a 30-mCi standard dose of radioiodine is not sufficient for a satisfactory thyroid ablation rate. Possible reasons for this failure may be the low 24-h radioiodine uptake, the low initial dose rate delivered to the residues, and the accelerated iodine clearance observed in EU patients. Possible alternatives for obtaining a satisfactory rate of thyroid ablation with rhTSH may consist of increasing the dose of radioiodine or using different protocols of rhTSH administration producing more prolonged thyroid cells stimulation.