Prognostic role of Tc-99m pertechnetate thyroid scintigraphy prior to fixed-dose radioiodine therapy of toxic multinodular goiters

Abstract

Aim: To investigate the prognostic role of Tc-99m pertechnetate thyroid scintigraphy pretreatment in patients with toxic multinodular goiters (TMNG) who were then treated with fixed I-131 doses. Materials and methods: We retrospectively evaluated 28 patients (18 females and 10 males; mean ± SD = 63 ± 11 years) that were treated with 740 megabecquerels (MBq) of I-131 for TMNG. Information, including age, Tc-99m pertechnetate thyroid scintigraphy and ultrasonography findings, antithyroid medication, thyroid hormone profile, and clinical status before treatment, was recorded. Th e regions of interest were drawn over the hot nodules, salivary glands, and the background on the anterior thyroid images. Th e net nodule counts, net salivary counts, nodule-to-salivary ratios, and nodule-to-background ratios were then calculated. The data were statistically compared for the hypothyroid and euthyroid patient groups after radioiodine treatment. Results: In the study group, the mean follow-up period was 7 ± 2 months (range: 6-12 months). We detected hyperthyroidism in 1 patient, euthyroidism in 19 patients, and hypothyroidism in 8 patients. Th e pretreatment mean net nodule counts (34.79 ± 14.06 counts) in the patients that developed hypothyroidism were significantly higher than in those patients that developed euthyroidism (26.80 ± 11.04 counts) (P = 0.014). The other 3 parameters did not show significant differences between the 2 groups. Conclusion: Th e Tc-99m pertechnetate uptake level of hot nodules calculated from the pretreatment of thyroid scintigraphy in patients with TMNG treated with a fixed 740-MBq I-131 dose may predict early hypothyroidism in patients. © TÜBİTAK.