Five months' follow-up of patients with and without iodine-positive lymph node metastases of thyroid carcinoma as disclosed by super(131)I-SPECT/CT at the first radioablation

Purpose: In differentiated thyroid carcinoma (DTC), super(131)I-SPECT/CT is more accurate in identifying radioiodine-positive lymph node metastases (LNM) than planar whole-body scans (WBS). The purpose of this study was to investigate the value of super(131)I-SPECT/CT performed at the first radioablation to predict the occurrence and/or persistence of cervical radioiodine-positive LNM 5months later. Methods: The study included 81 DTC patients that had had SPECT/ spiral CT after radioablation of thyroid remnants after thyroidectomy. The patients were re-examined 5months later using super(131)I-WBS performed at TSH stimulation. In addition, SPECT/CT of the neck was performed in patients with iodine-positive cervical foci to distinguish between thyroid remnant and LNM. The outcome variable of the study was the detection or exclusion of iodine-positive cervical LNM. Results: Of 61 patients without a SPECT/CT diagnosis of super(131)I-positive LNM at radioablation, 60 had no super(131)I-positive LNM at follow-up. In the remaining patient of this group, a new radioiodine-positive LNM was detected. In 17 of 20 patients with a SPECT/CT diagnosis of super(131)I-positive LNM (n=19) or an indeterminate lesion (n=1) at first radioablation, no super(131)I-positive LNM were detected 5months later. Radioiodine-positive LNM persisted in three patients of this group. Conclusion: super(131)I-SPECT/CT has a high negative predictive value with regard to the occurrence of radioiodine-positive cervical LNM 5months after initial therapy. The majority of iodine-positive LNM diagnosed by SPECT/CT at radioablation disappear within 5months. These findings motivate further research into the value of super(131)I-SPECT/CT of the neck for predicting recurrence and planning surgical reintervention in DTC.