Clinical outcome of hyperthyroid patients with functional autonomy after individualized radioiodine treatment

Abstract

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Objectives: This study aimed to evaluate the clinical outcome of patients affected by uni or multifocal autonomy of thyroid gland treated with an individualized radioiodine therapy in order to achieve euthyroidism.

Methods: One hundred and nine patients (age 67+/-10 yrs; 78F and 31M) affected by uni (44%) or multifocal (56%) autonomy were studied. Before 131I therapy patient accurate medical history was collected about hormonal status and previous treatments (percutaneous ethanol injections and/or antythyroid drug cycles). Each patient underwent a pretreatment dosimetric study to calculate the 131I activity to administer for therapy, based on repeated measurements of uptake (5 time-points) with a gammacamera after 123I administration. The same study was performed after therapeutic administration of 131I to calculate the real delivered dose. Patients were antithyroid drug free for at least one month before dosimetry and therapy. Each patient was required to check the serum levels of TSH, FT3 and FT4 once a year after therapy.

Results: The mean administered activity and the mean delivered target dose were 364+/-129 MBq [range 111-625 MBq] and 145+/-45 Gy [range 59-311 Gy] respectively. The mean follow-up was 2.9+/-1.8 years with a maximum of 5 years, and more than 71% of patients for each follow up time point were monitored. An almost stable euthyroidism incidence rate of 85% was reached after the first year, while 13 patients became hypothyroid and 6 remained in a hyperthyroid status. No significant differences were found in the 3 groups of patients about the pre 131I treatment clinical status and previous treatments, as well as about the administered activities and target doses.

Conclusions: Our clinical data showed that 131I activities and target doses lower than those reported in the literature may be administered to obtain excellent clinical outcome in patients with uni or multifocal thyroid autonomy. Few unsuccessful treatments were observed and no significant differences in pretreatment conditions or administered doses were found in comparison with euthyroid patients.