LONG-TERM FOLLOW-UP OF THYROID SCINTIGRAPHIES AFTER I-131 THERAPY OF SOLITARY AUTONOMOUS THYROID-NODULES

The aim of the present study was to assess thyroid scintigraphies afte r I-131 treatment of autonomous thyroid nodules with respect to evolut ion of the hot nodules as well as the extranodular tissue. A Tc-99m pe rtechnetate scintigraphy was carried out 1-16 years (median 8 years) a fter I-131 treatment of a solitary autonomous nodule in 66 patients re maining euthyroid. At the time of diagnosis, 9 of the patients were eu thyroid and 57 were hyperthyroid, of whom 27 received antithyroid drug therapy prior to I-131 treatment. The scintigraphies were evaluated t wice by 4 specialists (3 endocrinologists and 1 specialist in nuclear medicine). There was total agreement between the 4 observers in 50 and 52% in the first and second evaluation, respectively. The interobserv er variation was evaluated by means of omega coefficients and omega ra nged from 0.18 to 0.76 indicating poor to substantial agreement. A sol itary autonomous nodule with suppression of the extranodular thyroid t issue persisted in 50% of the patients, whereas a solitary cold nodule , homogeneous uptake or inhomogeneous uptake was found in 15, 22, and 13%, respectively. We conclude that although euthyroidism is achieved by radioiodine treatment, a hot nodule suppressing the Tc-99m pertechn etate in the extranodular tissue is still found in 50% of the patients even when serum TSH has been normal for years. Antithyroid drug thera py prior to I-131 treatment was more frequent in this group of patient s.