Nuclear medicine in the management of thyroid disease

Abstract

Thyroid disease management has changed little over the last 60 years and recent work suggests that the older approach remains the most effective. Treatment of benign hyperthyroidism has shown that functional imaging is essentially linked to therapy and uptake of iodine-131 ((131)I) cannot be assumed but should be tested by pre-imaging with radio-isotopes as 10% of patients may not be suitable for (131)I therapy and 1% may have a co-existent cancer. Differentiated thyroid cancer remains unique in that it is almost alone among common solid tumors in that it is routinely cured even if cannot all be removed by surgery. This is achieved in the majority of patients by a treatment introduced in the 1940s and does not involve the use of chemotherapy drugs but a simple and cheap isotope preparation; (131)I. However, in some differentiated thyroid cancers there is no accumulation of (131)I and we know this is due to the loss, or downregulation of the sodium iodide symporter gene. This has led to the development of several strategies to overcome this loss/downregulation, for example with the use of lithium or retinoids or gene treatment. However, all these approaches have yet to be proved in a randomized controlled trial. Advances in imaging especially using (18)F-fluorodeoxy-glucose PET has enabled patients with thyroid cancer to be more accurately imaged, resulting in a greater chance of cure through surgery and external-beam radiotherapy, especially if uptake of (131)I is poor. Another approach has been the idea of using radiolabeled somatostatin analogs, which are able to demonstrate uptake in the tumor and, more recently, beta-emitting isotopes have been used for therapy when other options have failed. Therefore, whilst the treatment of differentiated thyroid cancer is, to some degree, 60 years old, new methods have been proposed and are now being tested in this disease.

Molecular Optical Imaging with Radioactive Probes

“…Iodine ion accumulates in the thyroid, and Na 123/131 I has been widely used for imaging thyroid function and sodium iodide symporter as well as for treating thyroid cancer [12], [13], [14]. We tested the SPECT probe, Na 131 I, for thyroid radioactive OI.…”

Nuclear imaging of molecular processes in cancer

“…The imaging and treatment of thyroid cancer using radioiodine 131 I in the form of iodide marked the start of the field of nuclear medicine more than half a century ago, and remain central to the activities of nuclear medicine departments today [86]. Iodide ions accumulate in normally functioning thyroid tissue via the sodium/iodide symporter ("NIS"), which actively and avidly imports iodide into thyroid cells, followed by the incorporation and storage of iodine into thyroid hormones ("organification").…”

Preclinical Imaging for the Study of Mouse Models of Thyroid Cancer

“…Over the past several decades, nuclear medicine has played a central role in both imaging and therapy of human thyroid cancer patients [ 64 , 65 ]. Indeed, the ability to target the sodium/iodide symporter (NIS) with radioiodine has been the basis for nuclear medicine and therapy in human thyroid carcinoma [ 50 ].…”

“…The HFUS evaluation allowed for the detection of the normal thyroid in the subhyoid region and the diffuse enlargement of the gland in the propylthiouracil-treated mice [ 59 ]. The technique allowed for the detection of 19 nodules in the Tg-TRK-T1 mice, of which 11 were deemed to be malignant; the histological analysis could identify 17 of the HFUS-detected 19 nodules and malignancy was confirmed in 10 out of 11 [ 65 ]. In summary, the HFUS technique showed a sensitivity of 100% and a specificity of 60% in detecting nodules and a sensitivity of 91% and a specificity of 86% in diagnosing malignancy [ 59 ].…”