A case of stunning of lung and bone metastases of papillary thyroid cancer after a therapeutic dose (3.7 GBq) of¹³¹I and review of the literature: implications for sequential treatments

Abstract

Thyroid stunning is usually defined as the inhibition or suppression of iodide trapping by remnant thyroid tissue or by functioning metastases following a diagnostic dose of 131I. The risk of stunning increases progressively with larger doses. Because the threshold above which this effect occurs in thyroid remnants seems to be between 37 MBq and 111 MBq of 131I, therapeutic 131I doses of 3.7 GBq may cause stunning. We describe stunning of papillary thyroid cancer lung and bone metastases after a therapeutic dose of 131I (3.7 GBq). A T1 bone metastasis and bilateral lung metastases were diagnosed by post-therapeutic dose whole-body scan. Nuclear MRI detected another lesion at T4, whose 131I fixation was not obvious. An additional 0.7 GBq were given after recombinant TSH, 37 days after the therapeutic dose; 24 h later, uptake by the lung and T1 metastases had disappeared, but trapping was again seen 6 months later on the post-therapeutic scan. This re-appearance is evidence in favour of the transitory and reversible character of stunning, and confirms its correspondence to the decreased ability of viable thyroid cells to trap iodine and not to their destruction. A better understanding of stunning would make it possible, in the event of rapidly progressing disease and in conjunction with recombinant thyroid stimulating hormone (TSH), to give several therapeutic doses of 131I in close succession without each dose hampering the effectiveness of the subsequent one.

Micrometastasis of papillary thyroid carcinoma in a human immunodeficiency virus-infected patient: a case report and discussion

“…A stunning effect related to the 150 Mbq diagnostic dose is also open to question. This effect seems more closely related to the 131 I dose and has been described after diagnostic doses of 131 I, and in cases of remnant thyroid or functioning metastases [4,5]. In our patient, the diagnostic and therapeutic doses given after thyroid replacement hormone withdrawal showed persistence of iodine uptake in the neck and mediastinum areas.…”

Reappraisal of the indication for radioiodine thyroid ablation in differentiated thyroid cancer patients

“…There is an increasing trend to avoid diagnostic RAI WBS because of its low impact on the decision to ablate and because of concerns over 131 I-induced stunning of normal thyroid remnants [68] and distant metastases from thyroid cancer [69,70]. The alternative radiopharmaceutical for staging, 123 I, is not readily available and has a short halflife [71].…”

The Effect of Diagnostic Absorbed Doses from 131I on Human Thyrocytes in Vitro

“…Although the authors of several reports have investigated “thyroid stunning” conditions in vivo , i.e. , in patients subjected to the radioiodine treatment [ 9 , 10 , 12 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ], the molecular mechanisms of this phenomenon remain poorly characterized. The thyroid gland has the ability to concentrate iodide, which is then utilized to synthesize thyroglobulin and thyroid hormones.…”