Evaluation of whole-body retention of iodine-131 (131I) after postoperative remnant ablation for differentiated thyroid carcinoma – thyroxine withdrawal versus rhTSH administration: A retrospective comparison

Abstract

Abstract. Previous studies demonstrated that preparation with recombinant human thyroid-stimulating hormone (rhTSH) for thyroid remnant ablation results in lower extrathyroidal radiation compared to hypothyroidism. The results of 50 radioiodine therapies (RITs) under rhTSH, regarding iodine half-life, were evaluated and compared with 50 RITs performed on patients with hypothyroidism following thyroxine withdrawal. The patients were treated with 3700 MBq (100 mCi) of 131 I. Forty-eight hours after RIT, patients were measured with a radiation detector at a 1-meter (m) distance for evaluation of the effective dose (µSv/h). TSH and thyroglobulin (Tg) maximal values were also compared. rhTSH-stimulated patients had a significantly lower whole-body retention of 131 I (8.5±7.3 µSv/h), extrapolated from the measurements of the effective dose at a 1-m distance, compared to endogenously stimulated patients (13.6±8.1 µSv/h; p=0.001). Furthermore, TSH mean and Tg median levels were significantly higher in the rhTSH-stimulated patients (89.9±15.3 mU/l and 7.7 ng/ml, respectively) compared to the hypothyroid group (59.2±25.1 mU/l and 3.3 ng/ml; p<0.001 and p=0.003, respectively). Compared to thyroid hormone withdrawal, the use of rhTSH prior to RIT was associated with significantly lower whole-body retention of 131 I and with greater efficacy in reaching TSH levels greater than 30 mU/l, confirming data previously described.

Clinical Significance of Diffuse Intrathoracic Uptake on Post-Therapy I-131 Scans in Thyroid Cancer Patients

“…The mean TSH level of the negative intrathoracic uptake group patients who used rh-TSH (171.5±14.1) was significantly different from that of the negative thoracic uptake group who underwent hormone withdrawal (67.7±14.6) (p =0.001), suggesting that this was due to the use of rh-TSH. It has been reported that the use of rh-TSH produces higher TSH levels compared to thyroid hormone withdrawal [26]. Actually, the TSH level of the indeterminate uptake group of hormone withdrawal patients was higher (76.9±9.8) than that of the negative intrathoracic uptake group of hormone withdrawal patients (67.7±14.6); this was not statistically significant (p =0.081).…”

Thyroid Uptake and Effective Half-Life of Radioiodine in Thyroid Cancer Patients at Radioiodine Therapy and Follow-Up Whole-Body Scintigraphy Either in Hypothyroidism or Under rhTSH

“…Second, whole-body scintigraphy for response assessment is associated with low radiation exposure and currently in our clinic done almost exclusively with rhTSH. Table 7 compiles publications comparing the effect of hypothyroidism and rhTSH on whole-body dose, half-life, or residence time (6)(7)(8)(9)(10)(11)(12)(13)(14)(15). Most publications are based on studies with a limited number of patients.…”

“…Currently, RITh is often given 2-3 wk after surgery (1). Previous studies found differences in radiation exposure between patients treated in hypothyroidism versus rhTSH (6)(7)(8)(9)(10)(11)(12)(13)(14)(15). The aim was to retrospectively examine thyroid uptake and effective half-life in patients with a shorter time interval between surgery and RITh, thus reflecting current therapeutic standards.…”

Cytotoxic and genotoxic effects of 131I and 60Co in follicular thyroid cancer cell (WRO) with and without recombinant human thyroid‐stimulating hormone treatment

“…This type of tumor includes, basically, well‐differentiated papillary thyroid carcinoma (PTC) and follicular thyroid carcinoma (FTC), poorly differentiated carcinoma, and the most dedifferentiated, aggressive thyroid cancer, anaplastic thyroid carcinoma (ATC): all of them arise from one cell type, the thyroid follicular epithelial cell [Saiselet et al, ]. The predominant types of thyroid cancers, however, are PTC, which accounts for more than 80% of all thyroid malignancies, and FTC, for 10% of the well‐differentiated thyroid cancers [Carvalho et al, ].…”