Radiometabolic treatment of hyperthyroidism with a calculated dose of 131-iodine: results of one-year follow-up

What is the best definitive treatment for Graves' disease? A systematic review of the existing literature

BACKGROUND

The management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists for Graves' disease (GD) include any of the following modalities: (131)I therapy, antithyroid medication, or thyroidectomy. No in-depth analysis has been performed comparing the treatment options, even though a single treatment option seems to be universally accepted.

METHODS

A systematic review of the literature was performed to examine contemporary literature between 2001 and 2011 evaluating the management options of GD. We compiled retrospective and prospective studies analyzing surgery and radioactive iodine. Outcomes of interest included postoperative hypothyroidism, euthyroidism, and persistent or recurrent hyperthyroidism without supplementation. Success was defined as postoperative euthyroidism or hypothyroidism. Failure was defined as persistent or recurrent hyperthyroidism.

RESULTS

Of the 14,245 patients, 4,546 underwent surgery [3,158 patients had subtotal thyroidectomy (STT) and 1,388 had total thyroidectomy (TT)] and 9,699 had radioactive iodine. The radioactive iodine group consisted of 2,383 patients receiving 1-10 mCi, 1,558 patients receiving 11-15 mCi, 516 patients receiving >15 mCi, and 5,242 patients receiving an unspecified amount. Surgery was found to be 3.44 times more likely to be successful than radioactive iodine (p < 0.001). STT and TT were found to be 2.33 and 94.45 times more likely to be successful than radioactive iodine (p < 0.001), respectively.

CONCLUSIONS

On the basis of the outcomes analyzed, surgery appears to be the most successful in the management of GD, with TT being the preferred surgical option.

Striving for euthyroidism in radioiodine therapy of Graves' disease: a 12-year prospective, randomized, open-label blinded end point study

BACKGROUND

In China, use of radioiodine therapy is problematic because of the need for lifelong levothyroxine substitution. Our aim was to find an optimum dosing strategy for (131)I treatment of hyperthyroidism due to Graves' disease (GD). We attempted to achieve euthyroidism to avoid long-term levothyroxine treatment.

METHODS

Six hundred patients with GD were randomized into five groups, each comprising 120 individuals, to receive an individual (131)I activity selected from five different ascending activity ranges. The ranges were modulated according to a clinical score system. Follow-up was extended over a 12-year time frame. The primary outcomes were euthyroidism, hyperthyroidism, hypothyroidism, and recurrent hyperthyroidism. The secondary endpoint was the accumulated (131)I activity needed to achieve euthyroidism.

RESULTS

Out of 682 screened patients, 600 entered the study in 1997. Five hundred twenty-nine completed the last follow-up visit at the end of the study in 2009. Group 3 was identified as the study arm that received the optimum radioiodine activity, with 71.8% of the patients maintaining a euthyroid status, 5.8% remaining hyperthyroid, and 22.3% becoming hypothyroid by the end of the study. This group received 1.85-4.07 MBq per gram of thyroid tissue (average administered activity 261 ± 162 MBq). Over the 12-year follow-up period, the recurrence rate was 13.6%. The efficacy of (131)I treatment was related to activities modulated by a clinical score (χ(2) = 82.1, p = 0.000).

CONCLUSION

Our protocol effectively treated hyperthyroidism and significantly reduced the hypothyroidism rate. It may be preferable to the intentional induction of permanent hypothyroidism recommended by many experts.

The dilemma of how to manage Graves' hyperthyroidism in patients with associated orbitopathy

CONTEXT

Graves' orbitopathy (GO) is present in about 50% of patients with Graves' hyperthyroidism. It may range from mild to moderately severe and (rarely) to sight-threatening. Whether antithyroid drugs (ATDs), radioactive iodine (RAI), or thyroidectomy should be the treatment of choice in the presence of overt and active GO is a matter of debate.

EVIDENCE ACQUISITION

The major source of data acquisition included PubMed search strategies. Articles published in the last 30 yr were screened. Furthermore, the bibliographies of relevant citations and chapters of major textbooks were evaluated for any additional appropriate citation.

EVIDENCE SYNTHESIS

Prompt restoration and stable maintenance of euthyroidism is important for the course of GO. ATDs and thyroidectomy per se do not influence the natural history of GO. RAI can cause progression or de novo development of GO, particularly in smokers. This effect can be prevented by oral steroid prophylaxis. In patients with mild orbitopathy, the choice of thyroid treatment is largely independent of GO. Moderate-to-severe and active GO should be treated without delay. Whether in these patients, concomitant treatment of hyperthyroidism should be conservative (ATDs) or ablative (RAI, thyroidectomy, or both) is presently based on expert opinion rather than evidence. Emerging and potentially interesting biological agents, such as rituximab, counteracting pathogenic mechanisms of both hyperthyroidism and GO, need to be evaluated in randomized clinical trials.

CONCLUSIONS

The choice of the optimal treatment for hyperthyroidism in patients with moderate-to-severe and active GO remains unsettled and is mainly based on personal experience. Randomized clinical trials in this field are eagerly needed.

A study of the efficacy of radioiodine therapy with individualized dosimetry in Graves' disease: need to retarget the radiation committed dose to the thyroid

Although Iodine-131 (131I) therapy is fully validated for Graves' disease (GD), there is debate about radioiodine amount to be administered (prescribed activity), as well as the use of individualized dosimetry vs fixed 131I activity. The clinical outcome of 119 GD patients treated with 131I from 2003 to 2008 has been evaluated. The prescribed activity was calculated according to a dosimetric protocol taking into account several variables, including thyroid volume reduction during treatment. In addition, we performed a simulation according to other dosimetric protocols, by calculating the corresponding prescribed activities. The patients were followed up for at least 12 months after treatment. In the first period of observation (2003), a 120-200 Gray (Gy) radiation dose to the thyroid was prescribed, according to the guidelines published by the Italian Societies of Endocrinology, Nuclear Medicine and Medical Physics: hyperthyroidism cure with a single radioiodine administration was obtained in 53% of patients. This outcome raised up to 89% when a higher radiation dose to the target (200- 250 Gy) was prescribed, although the administered activities were still lower, as a rule, than the most commonly employed fixed activities (400-600 Mega-Becquerel--MBq). Our method showed a high level of individual dose optimisation, particularly when compared to simplified methods. In conclusion, the protocol adopted in this study ensures a satisfactory rate of hyperthyroidism cure, while administering quite low 131I activities, provided that an adequate committed radiation dose to the thyroid is prescribed. In this context, the dose indication given by the aforementioned guidelines should probably be revised.