Influence of the thyroid remnant in the elevation of the serum thyroglobulin after thyroidectomy in differentiated thyroid carcinoma. Importance of the diagnostic iodine total-body scanning

Abstract

We propose to perform periodic diagnostic TBS to improve Tg specificity, at least while neck thyroid activity is detected, even if Tg is negative.

Clinical outcomes of persistent radioiodine uptake in the neck shown by diagnostic whole body scan in patients with differentiated thyroid carcinoma after initial surgery and remnant ablation

“…The least differentiated metastases have been reported to be associated with lower Tg levels, because of a decrease in the synthesis or release of a normal Tg and the synthesis of immunologically inert Tg unrecognized by antibodies used in the routine assay, or the more rapid clearance of Tg from the plasma 14 . Of our 572 patients, 13 showed positive scans with undetectable Tg and negative TgAb, a rate similar to that previously reported 14–16 . None of our patients showed later Tg elevation, and there was no evidence of recurrent/persistent disease in any of the patients without abnormal US findings during a follow‐up of 47–100 months.…”

“…None of our patients showed later Tg elevation, and there was no evidence of recurrent/persistent disease in any of the patients without abnormal US findings during a follow‐up of 47–100 months. Another study reported that 13 of 128 patients showed evident neck activity with undetectable Tg and negative TgAb, with none showing evidence of later Tg elevation 15 . These results suggested that such patients were not considered to have false‐negative Tg reading.…”

Clinical Significance of Observation without Repeated Radioiodine Therapy in Differentiated Thyroid Carcinoma Patients with Positive Surveillance Whole-Body Scans and Negative Thyroglobulin

“…Previous reports ignored the clinical significance of radioiodine uptake in the thyroid bed after remnant ablation because of low thyroglobulin levels, which is considered a good prognostic marker [2,11-13]. However, a few recently published reports emphasized the importance of WBS [6-8]. One report concerning positive post-therapeutic WBS uptake outside the thyroid bed and negative thyroglobulin levels suggested metastatic lesions rather than false-positive image findings [7].…”

“…Another report demonstrated that many patients were positive for thyroid bed uptake on DxWBS and negative for Tg levels after high-dose RAI. These patients responded well to additional high-dose RAI therapy, discouraging the use of a negative Tg value as an adequate solitary marker for the presence and treatment of small cervical remnants [6]. …”

“…This information has shifted the focus back on the importance of WBS [6,7]. On the other hand, previous findings have considered thyroid bed uptake in WBS after total thyroidectomy and remnant ablation to be clinically insignificant and evidence of remnant ablation failure without regard to persistence/recurrent lesions in DTC [2].…”