Nuclear Medicine in the Management of Thyroid Disease

John Buscombe; Hassan Hirji; Caroline Witney-Smith

Disclosures

Expert Rev Anticancer Ther. 2008;8(9):1425-1431. 

In This Article

Abstract and Introduction

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 (131I) cannot be assumed but should be tested by pre-imaging with radio-isotopes as 10% of patients may not be suitable for 131I 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; 131I. However, in some differentiated thyroid cancers there is no accumulation of 131I 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 18F-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 131I 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, ß-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.

Introduction

Thyroid diseases represent the most common form of endocrine tumor with both benign and malignant tumors outnumbering any other type of tumor. As an endocrine tumor the benign form can be symptomatic with excessive production of thyroxine, producing a so-called 'toxic adenoma'. Malignant thyroid cancer has an incidence of ten per 100,000 in women and three per 100,000 in men in Europe[1] with a distribution that reflects the availability of iodine. The higher incidence of the follicular type in the Alps is being reversed by 40 years of iodine supplementation but replaced by a higher incidence of papillary tumors. Meanwhile, there remains a high incidence of follicular tumors in the area surrounding the Baltic, an almost iodine-free sea. In addition, the majority of eastern European countries have reported an increase in incidence of papillary thyroid cancer, some of which can be attributed to increased use of dietary iodine and some on the Chenobyl nuclear accident.[1–3] The great increase in young people traveling from eastern Europe and even further afield to live, study or work within the developed world has led to countries such as the UK being exposed to levels of thyroid disease normally only observed in continental Europe. For these reasons a review such as this is a timely reminder of the issues involved in the treatment of thyroid disease.

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