Thyroid echogenicity predicts outcome of radioiodine therapy in patients with Graves' disease.
BACKGROUND
Despite accounting for variations in gland size and iodine kinetics, the success of radioiodine therapy in patients with Graves' disease remains moderately common and unpredictable.


OBJECTIVE
We hypothesized that hypoechogenic glands, with large, densely packed cells, are more radiosensitive than normoechogenic glands, in which much radiation is wasted on more abundant colloid. We evaluated this hypothesis in a cohort of patients with Graves' disease.


METHODS
This was a prospective trial of patients recruited during 4 yr and followed up 1 yr after radioiodine therapy.


METHODS
This trial was held in a university hospital-outpatient clinic.


METHODS
A total of 177 consecutive patients with first presentation of Graves' disease (28 males), 23-76 yr old, who relapsed after antithyroid therapy were included in the study.


METHODS
The patients were assigned to an ablative target-absorbed dose of 200 Gy (n = 78) or randomly to 100 or 120 Gy of nonablative dose (n = 99).


METHODS
The measures were incidences of hyperthyroidism, euthyroidism, and hypothyroidism at 12-month follow-up.


RESULTS
At follow-up there were 25 hyperthyroid, 44 euthyroid, and 108 hypothyroid patients. Compared with 96 patients with a hypoechogenic gland, in 81 patients with a normoechogenic gland, there were more hyperthyroid (22 vs. 7%) and euthyroid (41 vs. 11%), but less hypothyroid outcomes (37 vs. 81%; P < 0.0001). The other independent predictor of increased radioresistance was the large gland volume.


CONCLUSIONS
In patients with Graves' disease, normoechogenic and large glands are associated with increased radioresistance.
Markovic
Vinko
V
Department of Nuclear Medicine, University Hospital Split, 21 000 Split, Croatia.
Eterovic
Davor
D
D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006111:Graves Disease / Q000175:diagnosis* / Q000532:radiotherapy*; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009929:Organ Size / Q000528:radiation effects; D011379:Prognosis; D011879:Radiotherapy Dosage; D016879:Salvage Therapy; D013961:Thyroid Gland / Q000000981:diagnostic imaging* / Q000473:pathology*; D016896:Treatment Outcome; D014463:Ultrasonography
D007457:Iodine Radioisotopes