Abstract
Low-risk (LR) differentiated thyroid cancer (DTC) patients should be ablated or not, albeit, with small dose of radioiodine is highly controversial. We hypothesized that those LR DTC patients who were surgically ablated need no radioiodine remnant ablation (RRA). This study aims to evaluate the long-term outcome in these two groups of patients. Retrospective cohort study conducted from January 1991 to December 2012. Based on extent of surgical resection and histopathology, LR DTC patients were classified as Gr-1: 169 patients, who were surgically ablated; Gr-2: 153 patients, who had significant remnant in thyroid bed. Basal parameters were comparable between two groups except pretherapy 24 h radioiodine uptake (0.16 ± 0.01% vs. 5.64 ± 0.46%; P < 0.001). No patient received RRA in Gr-1; Gr-2 patients were administered 30 mCi 131I. Total number of events (recurrence, persistent, and progression of disease), with median follow up of 10.3 years, was observed in 10/322 (3.1%) of LR DTC patients. Only one patient had disease recurrence from Gr-1, who became disease-free after radioiodine therapy. Similarly, one patient from 126, who was ablated with single dose of RRA, had recurrence from Gr-2. However, 8/27 (29.7%) patients from Gr-2 had persistent disease; even two of them subsequently developed disease progression, who failed first-dose of RRA. The event-free survival rates were 99.4% and 94.1% (P = 0.006) in Gr-1 and Gr-2, respectively. RRA is an overtreatment in surgically ablated LR DTC patients. Successfully ablated RRA patients also had similar long-term outcome, however, those who failed, should be re-stratified as intermediate-risk category, and managed aggressively.
Highlights
Thyroid remnant tissue is any normal thyroid tissue or microscopic disease in the thyroid bed left out after total/ near-total thyroidectomy (NTT)
The two groups were found to be similar with respect to all the baseline characteristics except for pretherapy radioiodine uptake (RAIU) values (P < 0.001) for obvious reason
The factors associated with failure to achieve remission with single dose of Radioiodine remnant ablation (RRA) were analyzed
Summary
Thyroid remnant tissue is any normal thyroid tissue or microscopic disease in the thyroid bed left out after total/ near-total thyroidectomy (NTT). Radioiodine remnant ablation (RRA) is defined as ablation of this remnant thyroid tissue by administration of radioiodine (RAI) [1]. RRA has been accepted as the standard-of-care in the management of differentiated thyroid cancer (DTC) [2]. Achievement of successful surgical ablation is considered as the eutopic goal where no further RRA is required [3]. 131I whole body scan (Dx-WBS)/Ultrasonography (USG) of neck/raised stimulated-thyroglobulin (sTg > 10 ng/ mL), RRA is administered with the aim to achieve complete tissue ablation. Proponents of RRA argue that remnant ablation, (a) reduces the chances of recurrence by targeting the microscopic tumor foci, (b) provides an added advantage by increasing the sensitivity of Dx-WBS, and (c) simplifies the follow up by serial estimation of serum thyroglobulin (Tg) levels to detect recurrence [2]
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