Radioiodine ablation: when and how

Differentiated thyroid cancer (DTC) is the most common endocrine malignancy with the highest mortality although with appropriate treatment has a good long-term prognosis and cure rate. Over the last 30 years there is a worldwide trend showing an increasing incidence of thyroid cancer. In DTC patients, total thyroidectomy has been for many decades routinely followed by the administration of radioiodine (131I) activity to destroy remnant thyroid tissue. Several reasons are in favour to routine ablation of postoperative thyroid remnants. The combination of both surgery and radioiodine has proven as a safe and effective treatment, resulting in improved life expectation and reduced recurrence rate for DTC patients. Recently, however, 131I ablation is not uniformly recommended for cancers smaller than 10 mm, and its use is debated for papillary tumours with diameter between 10 and 20 mm. Indeed, the decision about subsequent 131I thyroid remnant ablation is recommended as "individualized and selective". Even if new evidence has emerged that provides additional support for performing 131I treatment, the possible presence of radioiodine-associated side effects should be not overlooked. Moreover, a lot of discussion has taken place as to whether, and to what extent, 131I may cause secondary malignancies. Blood-based dosimetry is important to avoid surplus bone marrow toxicity while treating DTC patients. In this regard, the availability of a genetically engineered version of recombinant human TSH (rhTSH) provides an alternative tool to enhance serum TSH levels without inducing hypothyroidism. The administration of rhTSH to thyroid cancer patients still on LT4 therapy promotes radioiodine uptake and thyroglobulin production by thyroid cells to an extent comparable with hypothyroidism, preserving patients' quality of life, increasing the renal clearance of 131I and decreasing both the whole body and the blood dose. In this review the authors will discuss the pros and cons of postoperative radioiodine-induced thyroid remnant ablation.