Clinical Experience with Recombinant Human Thyrotrophin (rhTSH) in the Management of Patients with Differentiated Thyroid Cancer

The purpose of this work was to gain clinical experience with and to identify the optimal conditions for the use of recombinant human TSH (rhTSH, commercially available as Thyrogen®) in the management of patients with differentiated thyroid cancer (DTC).

The study involved 22 patients for a total of 27 administration cycles of rhTSH, for either diagnostic (in 19 instances) and/or therapeutic purposes (in 8 instances). There were 19 patients with papillary cancer (folliculau variant in 4, columnar variant in 1) and 3 patients with follicular cancer (1 Hurtle cell variant). All patients had previously undergone total thyroidectomy and 1-5 cycles of¹³¹I-therapy. Thyrogen® was administered i.m. according to the suggested protocol: 0.9 mg i.m. on days 1 and 2, radioiodine on day 3.

Peak serum TSH levels between 68-237 μIU/mL were observed after rhTSH administration; these were on average 65% higher, on a patient-by-patient basis, than peak serum TSH observed after conventional withdrawal of thyroxine treatment in 19 patients, while in 3 patients they were 28% lower, but still in the potent stimulation range (86-94 μIU/mL). There was general agreement between imaging results obtained under rhTSH stimulation and those obtained on prior occasions during thyroxine withdrawal, although radioiodine uptake was interpreted as less intense following Thyrogen® administration. Of 18 patients undergoing rhTSH administration for diagnostic purposes, 11 patients had a negative radioiodine whole-body scan (WBS) and 7 had a positive WBS. Three of the WBS-negative patients were shown to be actually affected by tumor recurrence, respectively by PET with [¹⁸F]FDG (in 2 cases) and by post-¹³¹I therapy scan. Serum thyroglobulin (hTg) increased to abnormal levels following rhTSH stimulation in 3/7 of the WBS-positive patients as well as in 1/11 WBS-negative patients. In 3/7 WBS-positive as well as in 3/11 WBS-negative patients, serum hTg progressively rose under rhTSH stimulation, yet still remaining below 3 ng/mL. Post-¹³¹I therapy scans following Thyrogen® administration showed good radioiodine uptake in 7/8 patients, the single-unsuccessful case being most likely due to expansion of the iodine pool because of recent use of an iodinated contrast medium.

The overall results show the feasibility and practical advantages of employing rhTSH stimulation in the general clinical setting rather than thyroxine withdrawal in the management of DTC patients. Caution should be raised on the interpretation of the serum hTg response to such potent but short-lived TSH stimulation.