Recombinant human TSH-aided radioiodine treatment of advanced differentiated thyroid carcinoma: a single-centre study of 54 patients

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Abstract
We sought to evaluate the efficacy, biochemical effects, safety and outcome of recombinant human thyroid-stimulating hormone (rhTSH) as an adjunct to radioiodine treatment of advanced differentiated thyroid carcinoma (DTC). We also sought to determine whether rhTSH is useful as an adjunct to radioiodine treatment following isotretinoin re-differentiation therapy of DTC metastases that have lost function. Therefore, in 54 consecutive patients who had retained bulky metastatic and/or locoregional lesions of DTC despite the exhaustion of other therapeutic options, we gave one to four courses of two consecutive daily intramuscular injections of rhTSH, 0.9 mg, followed by a therapeutic activity of 131I per os on day 3. Fifty patients had received prior radioiodine treatment aided by l-thyroxine (T4) withdrawal. We included in the study 23 patients who had received a trial of isotretinoin therapy for re-differentiation of confirmed de-differentiated metastases. In a blinded, within-patient comparison of post-therapy whole-body scans after the first rhTSH-aided and latest withdrawal-aided treatments in patients with functional metastases at baseline, 18 of 27 (67%) scan pairs were concordant, four (15%) were discordant in favour of the rhTSH-aided scan and five (19%) were discordant in favour of the withdrawal-aided scan. In total, 37 (74%) of 50 paired scans were concordant, eight (16%) favoured rhTSH and five (10%) favoured withdrawal. All differences appeared to be attributable to clinical causes, not to any difference between endogenous and exogenous TSH stimulation. Reflecting the biochemical activity of rhTSH and the release of thyroglobulin (Tg) due to tumour destruction, median serum Tg concentration rose approximately fourfold between baseline and day 6 of the rhTSH-aided treatment course. rhTSH was well tolerated, with mostly minor, transient toxicity, except for neck oedema in three patients with neck infiltrates and pathological spine fracture in one patient with a large vertebral metastasis. At 6 months, complete response occurred in one (2%), partial response in 12 (26%) and disease stabilisation in 19 (40%) of 47 evaluable patients. The rate of complete + partial response was 41% and that of disease stabilisation, 30%, in the 27 evaluable patients with functional metastases at baseline; the corresponding rates were 10% and 55% in the 20 evaluable patients with non-functional metastases at baseline. Although within-patient comparison of early outcome after both modalities is limited by a significantly greater median number of courses and a greater median cumulative activity of radioiodine given under withdrawal, response to rhTSH-aided and withdrawal-aided treatment was similar in 23 (52%) of 44 evaluable patients, superior with rhTSH in 12 (27%) and superior with withdrawal in seven (16%). In two patients, a superior response was obtained after isotretinoin pretreatment and rhTSH and attributed to re-differentiation therapy. In conclusion, our study provides preliminary evidence that rhTSH safely and effectively aids radioiodine treatment of advanced DTC, and does so to an at least equivalent degree as does T4 withdrawal.