High pre-therapy [99mTc]pertechnetate thyroid uptake, thyroid size and thyrostatic drugs: predictive factors of failure in [131I]iodide therapy in Graves' disease.
OBJECTIVE
Several factors may interfere with the success rate of radioiodine therapy (RIT) in Graves' disease. Our aim was to evaluate, retrospectively, some of these factors in the outcome of RIT.


METHODS
Patient gender, age at diagnosis, ophthalmopathy, disease duration, thyroid size, drug used as clinical treatment, thionamide withdrawal period during RIT preparation, FT4, TSH and [99mTc]pertechnetate thyroid uptake prior to RIT were studied as potential interference factors for RIT success. Eighty-two Graves' disease patients were submitted to RIT after thionamide treatment failure. Prior to RIT, 67 patients were receiving methimazole and 15 propylthiouracil. Thirty-three patients received thionamides during RIT; in 49 patients the medication was withdrawn for 2-30 days. [99mTc]pertechnetate thyroid uptake was determined before RIT. Fixed doses of 370 MBq of [131I]iodide were administered to all patients.


RESULTS
Eleven patients became euthyroid; 40 became hypothyroid and 31 remained hyperthyroid. There was no association between outcome and age at diagnosis, gender, ophthalmopathy, pre-RIT FT4, TSH, antithyroid antibodies or thyrostatic drug. Multiple logistic regression showed higher probability of treatment success in patients with thyroid mass <53 g (odds ratio (OR)=8.9), with pre-RIT thyroid uptake <12.5% (OR=4.1) and in patients who withdrew thionamide before RIT (OR=4.9).


CONCLUSIONS
Fixed doses of 370 MBq of radioiodine seem to be practical and effective for treating Graves' disease patients with [99mTc]pertechnetate uptake <12.5% and thyroid mass <53 g. This treatment is clearly not recommended for patients with large goitre. In contrast to what could be expected, patients with a high pre-RIT thyroid uptake presented a higher rate of RIT failure.
Zantut-Wittmann
Denise E
DE
Endocrinology Division, Department of Internal Medicine, State University of Campinas-Campinas, São Paulo, Brazil. zantutw@fcm.unicamp.br
Ramos
Celso D
CD
Santos
Allan O
AO
Lima
Marcelo M O
MM
Panzan
Anita D
AD
Facuri
Fla Via O
FV
Etchebehere
Elba C S C
EC
Lima
Mariana C L
MC
Tambascia
Marcos A
MA
Camargo
Edwaldo E
EE
D000293:Adolescent; D000328:Adult; D000368:Aged; D013956:Antithyroid Agents / Q000627:therapeutic use; D001938:Brazil / Q000453:epidemiology; D002648:Child; D005260:Female; D006111:Graves Disease / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000378:metabolism / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D011379:Prognosis; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D013670:Sodium Pertechnetate Tc 99m / Q000493:pharmacokinetics; D017211:Treatment Failure; D016896:Treatment Outcome
D013956:Antithyroid Agents; D019275:Radiopharmaceuticals; D013670:Sodium Pertechnetate Tc 99m