Endocrine Abstracts

Background: To determine whether radioiodine remnant ablation (RRA) reduces cause-specific mortality (CSM) or tumor recurrence (TR) rates after bilateral thyroidectomy (BT) in low-risk adult papillary thyroid carcinoma (APTC) patients treated with curative intent, we compared outcome in 1836 stage I patients having BT alone with 832 having BT+RRA.

Methods: THEN cohort (1966-1990) comprised 809 patients; 36% having RRA within 6 postoperative months. NOW cohort (1991-2015) comprised 1859 patients (29% having BT+RRA); statistical analyses of differences in occurrence rates between BT alone and BT+RRA performed with SAS software.

Results: During 1966-90, when RRA rates rose tenfold, 20-year CSM and TR rates after BT alone were 0.6 and 7.9%; rates after BT+RRA higher at 1.2% (P = .66) and 11.7% (P = .04). When compared to rates after BT alone, RRA did not significantly improve CSM or TR rates at local, regional, or distant sites (P>.1). During 1991-2015, when RRA rates fell, no NOW cohort patient died of PTC. The 20-year TR rate after BT alone was 7.6%; after BT+RRA significantly higher at 20.0% (P<.0001). RRA in NOW cohort was administered to 49% of pN1 patients but only 17% of pN0/NX patients (P<.0001). TR rates were examined separately for node-negative and node-positive patients. In 1157 pN0 cases, 20-yr loco-regional recurrence (LRR) rates were 3.1% after BT and higher (P = .049) at 8.6% after BT+RRA. In 702 pN1 patients, 20-yr LRR rates were higher at 27.0% after BT+RRA, when compared to 19.4% after BT alone (P = .045); in four pN1 groups, stratified by nodal burden, RRA did not significantly (P>.5) reduce the LRR rates observed after BT with curative intent.

Conclusions: RRA given to adequately treated stage I patients did not reduce CSM or TR rates. Therefore, we do not recommend RRA for APTC patients who have stage I disease and undergo potentially curative BT.