The quality of life of thyroid cancer patients is improved with the use of recombinant human TSH (rhTSH) that avoids hypothyroidism, provides an effective stimulation of any thyroid tissue and does not increase the global cost of treatment and follow-up. Several consensus and guidelines have recently delineated indications for using rhTSH.
Post-operative radioiodine administration is not indicated for very low risk tumors (<1 cm, unifocal, intrathyroid); in case of persistent disease and in high risk patients, a high activity (3700 MBq) is given after thyroid hormone withdrawal; in the other patients, a high (3700 MBq) or a low (1100 MBq) activity may be given following withdrawal or following rhTSH. Further randomized studies are needed to assess the efficiency and the medico-economic impact of each of these 4 treatment modalities (high or low activities, withdrawal or rhTSH).
Cure is assessed at 912 months with a neck ultrasonography and a serum Tg determination obtained 3 days after rhTSH stimulation (0.9 mg im, on 2 consecutive days). A routine diagnostic TBS is not necessary. Low risk patients with a normal neck US and an undetectable rhTSH stimulated serum Tg are considered cured. The reliable assessment of cure permits reassurance of patients, the subsequent use of replacement doses of thyroxine and the simplicity of the subsequent yearly follow-up with serum TSH and Tg determinations. There is a close relationship between basal and TSH-stimulated serum Tg levels, and this was recently confirmed by using a supersensitive assay; however, the improved sensitivity of serum Tg determination on thyroxine treatment is observed at the expense of a decreased specificity and there is no evidence that TSH-stimulated Tg determination can be obviated to reliably assess cure.
Radioiodine treatment of distant metastases consists in administering a high activity (3700 MBq or more) following thyroid hormone withdrawal, every 6 to 12 months. Uptake in metastases is lower following rhTSH than withdrawal, but whole body radiation doses are also lower and this permits the administration of higher activities.