Guidelines for radioiodine therapy of differentiated thyroid cancer

Update on recent developments in the therapy of differentiated thyroid cancer

In the past decade, the management of differentiated thyroid carcinoma changed significantly and thus contributed to the improvement of the already favorable prognosis of this malignant disease. Surgical treatment techniques improved and the extent of initial surgery is more individualized. Radioiodine therapy is an essential part of therapeutic regimens in almost all cases, and the use of recombinant human thyroid-stimulating hormone has established for ablation of remnant tissue, treatment of iodine-positive cancer, and sensitive thyroglobulin measurement during follow-up. Risk stratification has become more important to plan treatment and follow-up individually, particularly to evaluate the need for thyroid-stimulating hormone suppression therapy. Especially for inoperable and radioiodine-negative thyroid carcinomas, novel treatment options such as tyrosine kinase inhibitor therapy have emerged. This article deals with the current options of optimal therapy regimens in differentiated thyroid carcinoma.

Iodine biokinetics and radioiodine exposure after recombinant human thyrotropin-assisted remnant ablation in comparison with thyroid hormone withdrawal

CONTEXT

A few prospective studies have evaluated the use of recombinant human TSH (rhTSH) for radioiodine remnant ablation.

OBJECTIVE

Our objective was to compare the effects of the both TSH regimens on iodine biokinetics in the thyroid remnant, dosimetry, and radiation protection.

DESIGN

We conducted a prospective randomized study.

MATERIALS AND METHODS

Eighty-eight patients were enrolled for radioiodine ablation to either the hypothyroid or rhTSH arms. A whole-body scan was performed at 48 and 144 h after therapy. Dose rates were assessed at 24, 48, and 144 h. Urinary samples were obtained during the first 48 h. Thyroglobulin was assessed before and after therapy. Iodine biokinetics in the remnants were calculated from gamma-count rates. Radiation-absorbed dose was calculated using OLINDA software. Exposure estimation was based on a validated model.

RESULTS

The effective half-life in the remnant thyroid tissue was significantly longer after rhTSH than during hypothyroidism (P = 0.01), whereas 48-h (131)I uptakes and residence times were similar. After therapy, thyroglobulin release (a marker of cell damage) was lower in the rhTSH arm. The mean total-body effective half-life and residence time were shorter in patients treated after rhTSH. Residence time was also lower for the colon and stomach. Absorbed dose estimates were lower in the rhTSH arm for the lower large intestine, breasts, ovaries, and the bone marrow. Dose rates at the time of discharge were lower in the rhTSH group with a reduction in cumulative radiation exposure to contact persons.

CONCLUSIONS

In comparison with thyroid hormone withdrawal, rhTSH is associated with longer remnant half-life of radioactive iodine while also reducing radiation exposure to the rest of the body and also to the general public who come in contact with such patients.

To stimulate or withdraw? A cost-utility analysis of recombinant human thyrotropin versus thyroxine withdrawal for radioiodine ablation in patients with low-risk differentiated thyroid cancer in the United States

CONTEXT

Use of recombinant human TSH (rhTSH) prior to radioactive iodine remnant ablation for patients with differentiated thyroid cancer avoids the hypothyroid state and improves quality of life. European studies have shown that use of rhTSH vs. thyroid hormone withdrawal is a cost-effective method for preparing patients for ablation.

OBJECTIVE

The objective of the study was to determine the cost-utility of rhTSH prior to ablation in the United States.

DESIGN/SETTING/SUBJECTS

A Markov decision model was developed for a hypothetical group of adult patients with low-risk differentiated thyroid cancer who were prepared for ablation by either rhTSH or thyroid hormone withdrawal. Patients entered the model after initial thyroidectomy; follow-up was in accordance with current American Thyroid Association guidelines. Input data were obtained from the literature, Medicare reimbursement schedule, and U.S. Bureau of Labor Statistics. Sensitivity analyses were performed for all clinically relevant inputs.

MAIN OUTCOME MEASURES

Cost-utility, measured in U.S. dollars per quality-adjusted life-year ($/QALY), was measured.

RESULTS

Use of rhTSH yielded an incremental cost-utility of $52,554/QALY (95% confidence interval $52,058-53,050/QALY) (incremental societal cost of $1,365/patient; incremental benefit of 0.026 QALY/patient). The majority of cost and benefit occurs during the preablation, ablation, and postablation period; differences in cost are due to cost of rhTSH and differences in productivity loss (days off work). The model was most sensitive to changes in time off work, cost of rhTSH, and differences in utilities of health states.

CONCLUSIONS

In the United States, the cost-effectiveness of rhTSH for ablation in patients with low-risk differentiated thyroid cancer is highly dependent on potential variations in cost of rhTSH, rates of remnant ablation, time off work, and quality of life.

Should we routinely offer a second admission for radioiodine to patients with high-risk differentiated thyroid cancer?

AIMS

To assess whether an elective second admission for radioiodine is useful for patients with high-risk differentiated thyroid cancer (DTC).

MATERIALS AND METHODS

A retrospective analysis was carried out on 47 high-risk DTC patients treated with a second admission for radioiodine at our centre during the 2007-2008 period.

RESULTS

In 21 patients (45%), the surgeon described an incomplete resection. Twenty-six (55%) had surgical macroscopic complete resection, but cancer cells at the margin of excision histologically. Overall, at the second admission for radioiodine, 27 patients (57%) had a normal post-treatment scan and undetectable thyroid-stimulating hormone (TSH) stimulated thyroglobulin. Twenty patients (43%) had raised stimulated thyroglobulin at second admission for radioiodine, of whom only six (13%) had abnormal uptake (>0.1%) on the post-treatment scan.

CONCLUSIONS

A second admission for radioiodine could have been avoided in most patients. Instead, information from stimulated thyroglobulin and a diagnostic radioiodine scan would have been sufficient to guide further management. This study also provides interesting outcome data on incompletely resected DTC.

Radioiodine ablation for differentiated thyroid cancer-none, one dose or two?

Patients with good prognosis differentiated thyroid cancer are at risk from over-treatment with radioiodine thyroid remnant ablation. Some with unfavourable localised disease might benefit from an elective second dose.

Natural history and clinical outcome of differentiated thyroid carcinoma: a retrospective analysis of 1503 patients treated at a single institution

BACKGROUND

The study evaluates clinical presentation and outcome of differentiated thyroid cancer (DTC) on a large series of patients homogeneously managed.

PATIENTS AND METHODS

A cohort of 1503 DTC followed according to a standardized protocol entered the study. Main outcome measures were clinical presentation at the diagnosis, survival, morbidity and prognostic risk factors.

RESULTS

Median age at diagnosis was 46 years. Papillary cancer and low pathological tumor-node-metastasis stages represented >80% of cases. Cancer specific survival at 5, 10 and 15 years was 98.6%, 94.7% and 87.4%; 10-year disease-free and progression-free survivals were 96.8% and 17.1%, respectively. Cancer-specific mortality rate was 2.5% [95% confidence interval (CI) 1.7% to 3.4%], recurrence rate was 0.6 % while morbidity rate was 12.6% (95% CI 11% to 14%). Response to radioiodine treatment is the strongest predictor of a good outcome in multivariate analysis (hazard ratio 211, P < 0.0001). Other independent predictor variables are sex, age, histology and distant metastases for survival and metastases for morbidity.

CONCLUSIONS

A rigorous initial therapeutic approach leads to a better survival and a very low morbidity. Patients who do not respond to radioiodine treatment have a worse prognosis.

Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer

BACKGROUND

Thyroid nodules are a common clinical problem, and differentiated thyroid cancer is becoming increasingly prevalent. Since the publication of the American Thyroid Association's guidelines for the management of these disorders was published in 2006, a large amount of new information has become available, prompting a revision of the guidelines.

METHODS

Relevant articles through December 2008 were reviewed by the task force and categorized by topic and level of evidence according to a modified schema used by the United States Preventative Services Task Force.

RESULTS

The revised guidelines for the management of thyroid nodules include recommendations regarding initial evaluation, clinical and ultrasound criteria for fine-needle aspiration biopsy, interpretation of fine-needle aspiration biopsy results, and management of benign thyroid nodules. Recommendations regarding the initial management of thyroid cancer include those relating to optimal surgical management, radioiodine remnant ablation, and suppression therapy using levothyroxine. Recommendations related to long-term management of differentiated thyroid cancer include those related to surveillance for recurrent disease using ultrasound and serum thyroglobulin as well as those related to management of recurrent and metastatic disease.

CONCLUSIONS

We created evidence-based recommendations in response to our appointment as an independent task force by the American Thyroid Association to assist in the clinical management of patients with thyroid nodules and differentiated thyroid cancer. They represent, in our opinion, contemporary optimal care for patients with these disorders.

Unexpected effect of furosemide on radioiodine urinary excretion in patients with differentiated thyroid carcinomas treated with iodine 131

BACKGROUND

In patients receiving (131)I for therapeutic purposes, diuretics are frequently used in an attempt to accelerate elimination of unbound radioiodine, reduce its adverse effects, and shorten the hospital stay. The aims of our study were to investigate the influence of furosemide therapy on urinary excretion of (131)I in patients with differentiated thyroid cancer (DTC), referred to radioiodine ablation after thyroidectomy, and to investigate whether diuretics are useful in daily practice in patients with DTC.

METHODS

Forty-three patients with DTC who had normal renal function and low (131)I uptake in cervical region (3.55 +/- 3.45%) were included in this study. The furosemide (20 mg) and potassium chloride (250 mg) were given orally to 23 patients 3 hours after the (131)I administration, and then q8h for 3 days. Twenty patients did not receive either furosemide or potassium chloride. After (131)I administration, the patients collected their urine for 3 days, and radioactivity of urine sample from each micturition was expressed as percentage of the administered dose. Radioactivity of blood samples was measured after 72 hours, and the values were corrected for decay of (131)I and expressed in relation to the administered dose. Initial whole-body measurement (immediately after (131)I administration) and the whole-body measurement after 72 hours were recorded for all patients. The 72-hour whole-body measurement was corrected for decay of (131)I, and expressed as a percentage of the initial whole-body measurement.

RESULTS

Urinary excretion of (131)I was significantly lower in the patients who were taking furosemide and potassium chloride compared with the control group. The whole-body measurements after 72 hours (13.22 +/- 6.55% vs. 8.24 +/- 3.39% of the initial; p < 0.01, respectively) and the blood radioactivity (34.66 +/- 24.84 vs. 11.64 +/- 8.32 cpm/mL per 1 MBq of administered (131)I, p < 0.01) were found to be unexpectedly higher in the patients who were taking furosemide and potassium chloride compared with the control group.

CONCLUSION

Our results demonstrated that furosemide given as an adjuvant medication in patients with DTC causes a significant decrease in urinary excretion of radioiodine and its higher blood concentration. Therefore, furosemide should not be recommended as an adjuvant therapy to radioiodine ablation in patients with DTC previously iodine depleted by low-iodine diet.

Clinical relevance of single-photon emission computed tomography/computed tomography of the neck and thorax in postablation (131)I scintigraphy for thyroid cancer

CONTEXT

In patients with differentiated thyroid carcinoma, postablation (131)I scintigraphy aims to detect residual neck disease and distant metastases, usually found in lungs and bones. New hybrid single-photon emission computed tomography/computed tomography (SPECT-CT) cameras that permit functional and anatomical image fusion may improve its clinical relevance.

OBJECTIVE

Our objective was to test the added value of neck and thorax SPECT-spiral CT to whole-body scan (WBS) in postablation (131)I scintigraphy.

DESIGN AND SETTING

This was a single-referral-center prospective study with a median follow-up of 21 months.

PATIENTS AND METHODS

Postablation (131)I WBS and neck and thorax SPECT-CT were performed in 55 consecutive patients treated in 2006. WBS and SPECT-CT data were blindly reviewed, scored negative (benign), positive (malignant), or indeterminate and were correlated to the patient outcome.

RESULTS

At patient level, WBS and SPECT-CT were negative in 67 and 78% of patients, positive in 4 and 15%, and indeterminate in 29 and 7%, respectively. Overall, nine patients (16%) presented treatment failure (persistent or recurrent disease) 1-16 months after radioiodine ablation. In the 16 patients with indeterminate WBS, negative SPECT-CT ruled out suspicion of disease in nine of nine patients, and positive SPECT-CT confirmed malignant lesions in four of five patients. Positive SPECT-CT predicted treatment failure better than positive WBS (McNemar's test, P = 0.03).

CONCLUSIONS

This study demonstrates the complementary role of neck and thorax SPECT-CT to WBS in postablation (131)I scintigraphy. Because SPECT-CT allows one to confirm or to rule out residual disease in most cases where WBS remains indeterminate, we recommend its use when available.

Radio-iodine therapy in differentiated thyroid cancer: indications and procedures

Post-surgical ablative iodine-131 therapy is recommended for all differentiated thyroid cancer primary tumors>1 cm in diameter. Regarding smaller primary tumors, 131I ablation may be helpful in special cases: tumor close to the thyroid capsule, previous percutaneous radiation to the neck, familial occurrence of thyroid cancer, tumor diameter 5-10 mm, and unfavorable histological variants. In this context, the patient's preferences for safety should be considered. In most centers, standard fixed activities of 1-3 GBq are used for 131I ablation. Preparation for the procedure with such activities requires a low-iodine diet for 2-3 weeks and stimulation of thyroid stimulating hormone (TSH) by withholding of thyroid hormone for 3 weeks following thyroidectomy or by use of recombinant human TSH. The advantages of recombinant TSH are avoidance of hypothyroid morbidity and consequently a better quality of life, as well as a lower radiation dose to extra-thyroidal compartments. To treat metastastic differentiated thyroid cancer, higher activities of radio-iodine (in the range 4-11 GBq) are necessary; if possible, individual dosimetry is recommended. The standard approach to preparation for 131I therapy in patients with metastases is endogenous hypothyroidism after thyroid hormone withdrawal.