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

Abstract

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. The regions of interest were drawn over the hot nodules, salivary glands, and the background on the anterior thyroid images. The 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. The 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: The 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.