Bexarotene increases uptake of radioiodide in metastases of differentiated thyroid carcinoma.
OBJECTIVE
Treatment options for metastases of differentiated thyroid carcinoma (DTC) are limited due to decreased uptake of radioiodide (I-131). Therefore, strategies to improve I-131 uptake are mandatory. It has been suggested that retinoids have beneficial effects on iodide uptake in vitro and in humans. However, to date, only studies with 13-cis-retinoic acid have been performed in humans. We therefore decided to study the effects of 6 weeks of treatment with the retinoid X receptor activator bexarotene on I-131 uptake in patients with metastatic DTC.


METHODS
Open prospective intervention study.


METHODS
Twelve patients with metastases of DTC, with insufficient uptake of I-131, received 6 weeks of treatment with 300 mg bexarotene/day. Prior to, and after this intervention, I-131 uptake was measured by whole-body scintigraphy and single photon emission tomography (SPECT) 3 days after 185 MBq I-131. Diagnostic imaging was preceded by two consecutive injections of recombinant human TSH.


RESULTS
Bexarotene treatment induced I-131 uptake in metastases of 8 out of 11 patients (one patient died for reasons not related to the study). However, uptake was only discernable at SPECT and had incomplete matching with metastases as visualized by CT scanning.


CONCLUSIONS
Bexarotene partially restores I-131 uptake in metastases of DTC. The clinical relevance of this observation may be limited due to the differential responses of the different metastases within each patient and the low intensity of I-131 uptake.
Department of Endocrinology, Leiden University Medical Center, The Netherlands.
Ying Y
YY
Liu
Marcel P
MP
Stokkel
Alberto M
AM
Pereira
Eleonora P
EP
Corssmit
Hans A
HA
Morreau
Johannes A
JA
Romijn
Johannes W A
JW
Smit
D000328:Adult; D000368:Aged; D000077610:Bexarotene; D002291:Carcinoma, Papillary / Q000532:radiotherapy / Q000556:secondary / Q000628:therapy; D002454:Cell Differentiation; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D008175:Lung Neoplasms / Q000556:secondary; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis / Q000532:radiotherapy*; D011994:Recombinant Proteins; D047488:Retinoid X Receptors / Q000187:drug effects / Q000502:physiology; D013764:Tetrahydronaphthalenes / Q000627:therapeutic use*; D013964:Thyroid Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000628:therapy; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D007457:Iodine Radioisotopes; D011994:Recombinant Proteins; D047488:Retinoid X Receptors; D013764:Tetrahydronaphthalenes; D014284:Triiodothyronine; D013972:Thyrotropin; D000077610:Bexarotene; D013974:Thyroxine