131I activity for remnant ablation in patients with differentiated thyroid cancer: A systematic review

An updated systematic review and commentary examining the effectiveness of radioactive iodine remnant ablation in well-differentiated thyroid cancer

Radioactive iodine remnant ablation (RRA) is used to destroy residual normal thyroid tissue after complete gross surgical resection of papillary or follicular thyroid cancer. The article updates a prior systematic review of the literature to determine whether RRA decreases the risk of thyroid cancer-related death or recurrence at 10 years after initial surgery, including data from 28 studies. No long-term randomized trials were identified, so the review is limited to observational studies. The incremental benefit of RRA in low risk patients with well-differentiated thyroid cancer after total or near-total thyroidectomy who are receiving thyroid hormone suppressive therapy remains unclear.

Low vs. high radioiodine activity to ablate the thyroid after thyroidectomy for cancer: a randomized study

Background

Radioactive iodine is commonly administered following thyroidectomy for differentiated thyroid carcinoma to ablate the thyroid remnant. The optimal administered activity of radioiodine is unknown.

Methodology/Principal Findings

Adult subjects (n = 160) diagnosed with papillary or follicular thyroid carcinoma were randomly allocated to receive either 1100 MBq (30 mCi) or 3700 MBq (100 mCi) activity of radioiodine (¹³¹I) following thyroidectomy. The study participants were prepared for ablation using thyroid hormone withdrawal. Ablation was considered successful when serum thyroglobulin concentration was less than 1 ng/mL and no uptake was present in ¹³¹I scan. Ablation was successful following one administration of radioiodine in 42 (52%; 95% CI, 41% to 63%) of the 81 evaluable study participants who received 1100 MBq, and in 43 (56%, 45% to 67%) of the 77 subjects who received 3700 MBq activity (P = .61). There was no difference between the groups in the numbers of repeat radioiodine treatments needed to complete ablation (P = .27). The higher activity was associated with more nausea and taste disturbances, and a longer stay in a radioprotected isolation unit. None of the participants died from thyroid cancer during a median follow up of 51 months; three subjects in the 3700 MBq group and none in the 1100 MBq group were diagnosed with distant metastases during follow-up. In a meta-analysis of four randomized studies that compared the 1100 and 3700 MBq activities, the 1100 MBq activity tended to be associated with a higher risk of unsuccessful ablation (relative risk 1.148, 95% CI 0.974 to 1.353, P =  .10).

Conclusions/Significance

The results provide no conclusive evidence that 3700 MBq activity is more effective for ablation of the thyroid remnant than 1100 MBq activity. The 3700 MBq activity is associated with more adverse effects.

Trial Registration

ClinicalTrials.gov NCT00115895

A quality-effects model for meta-analysis

We introduce a quality-effects approach that combines evidence from a series of trials comparing 2 interventions. This approach incorporates the heterogeneity of effects in the analysis of the overall interventional efficacy. However, unlike the random-effects model based on observed between-trial heterogeneity, we suggest adjustment based on measured methodological heterogeneity between studies. We propose a simple noniterative procedure for computing the combined effect size under this model and suggest that this could represent a more convincing alternative to the random effects model.

Regional differences in opinions on adjuvant radioactive iodine treatment of thyroid carcinoma within Canada and the United States

OBJECTIVE

To identify regional differences in recommendations for radioactive iodine remnant ablation (RRA) in early stage well-differentiated thyroid carcinoma (WDTC) within Canada and the United States.

DESIGN

A cross-sectional written survey of a sample of physicians in specialties potentially involved in thyroid cancer care was performed in 2006. Participants were asked if they recommended RRA for a hypothetical 38-year-old woman with a solitary, 1.6-cm papillary carcinoma resected by total thyroidectomy. Exploratory regional comparisons were performed using Student t tests or analysis of variance. The regions studied were western Canada, eastern Canada (Ontario, the Maritimes), Quebec, the northeastern United States, the western and midwestern United States, and the southern United States. In a secondary multivariable logistic regression analysis, we explored potential relationships between individual respondent characteristics RRA recommendations.

MAIN OUTCOME

Agreement with case-based RRA recommendations was measured on a Likert scale of 1 to 7 (7 = strongest agreement).

RESULTS

The effective response rate was 56.3% (486/864). There were significant differences in RRA recommendations among the regions studied (F = 11.99, 5 df, p < 0.001); national boundaries did not explain regional variations. For the sample case, the strongest support for RRA was in Quebec and the southern United States, intermediate support in eastern Canada and the northeastern United States, and the least support in western Canada and the western and midwestern United States. Academic affiliation and surgical specialty were independently inversely associated with strong RRA recommendations.

CONCLUSIONS

There are significant regional differences in physician-based RRA recommendations in early stage WDTC within Canada and the United States. Physician specialty and practice characteristics may influence RRA recommendations.

Management of low-risk differentiated thyroid cancer

OBJECTIVE

To summarize the definitions of and management recommendations for low-risk thyroid cancer made by the American and European Thyroid Associations and synthesize this information with the recent literature, including systematic evaluations of tumor staging systems guiding therapy.

METHODS

The American Thyroid Association and European Thyroid Association guidelines were compared and pertinent literature since 2005 was reviewed.

RESULTS

Of papillary thyroid microcarcinomas (PTMC), up to 50% breach the thyroid capsule, 64% have lymph node metastases, up to 43% are multifocal, and as many as 2.8% have distant metastases. Locoregional and distant recurrences are, respectively, as high as 5.9% and 1.5%. As many as 1 in 4 patients with a papillary thyroid carcinoma 1.5 cm or smaller develop persistent disease. Cancer-related mortality rates are usually less than 1%, but are as high as 2% in some reports. Tumor staging systems are too inaccurate to guide therapy.

CONCLUSION

It is unlikely that many patients will forgo treatment after understanding their risk, especially when total thyroidectomy and radioiodine (131I) therapy can reduce the PTMC recurrence or persistence disease rate to zero. Preoperatively diagnosed PTMC should be treated with total or near-total thyroidectomy, regardless of tumor size. For very low-risk patients with unifocal PTMC smaller than 1 cm that is removed by chance during surgery to treat benign thyroid disease, lobectomy alone without 131I therapy may be sufficient therapy if there are no concerning histologic features and no tumor extension beyond the thyroid, metastases, history of head and neck irradiation, or positive family history--any of which requires total or near-total thyroidectomy and remnant ablation with 30 mCi.

Nódulos de tireóide e câncer diferenciado de tireóide: consenso brasileiro

Os nódulos tireoidianos constituem a principal manifestação clínica de uma série de doenças da tireóide com uma prevalência de aproximadamente 10% na população adulta. O maior desafio é excluir o câncer da tireóide, que ocorre em 5 a 10% dos casos. Os carcinomas diferenciados respondem por 90% dos casos de todas as neoplasias malignas da tireóide. A maioria dos pacientes com carcinoma diferenciado apresenta, geralmente, um bom prognóstico quando tratada adequadamente, com índices de mortalidade similares à população geral. No entanto, alguns indivíduos apresentam doença agressiva, desafiando o conhecimento atual e ilustrando a complexidade do manejo dessa neoplasia. No presente trabalho, reunimos 8 membros do Departamento de Tireóide da Sociedade Brasileira de Endocrinologia & Metabologia, para elaborarmos, por consenso, as diretrizes brasileiras no manejo dos nódulos tireoidianos e do câncer diferenciado da tireóide. Os membros participantes representam diferentes Centros Universitários do Brasil, refletindo diferentes abordagens diagnósticas e terapêuticas. Inicialmente, cada participante ficou responsável pela redação de determinado tema a ser enviado ao Coordenador, que, após revisão editorial e elaboração da primeira versão do manuscrito, enviou ao grupo para sugestões e aperfeiçoamentos. Quando concluído, o manuscrito foi novamente enviado e revisado por todos. A elaboração dessas diretrizes foi baseada na experiência dos participantes e revisão pertinente da literatura.