Nuclear medicine in the management of thyroid disease

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.