Clinical Outcomes after Early and Delayed Radioiodine Remnant Ablation in Patients with Low-Risk Papillary Thyroid Carcinoma: Propensity Score Matching Analysis

• Main Authors: Jonghwa Ahn, Meihua Jin, Eyun Song, Min Ji Jeon, Tae Yong Kim, Jin-Sook Ryu, Won Bae Kim, Young Kee Shong, Ji Min Han, Won Gu Kim
• Format: Article
• Language: English
• Published: Academya Publishing Co. 2020-12-01
• Series: Endocrinology and Metabolism
• Subjects: thyroid neoplasms; thyroid cancer; papillary; iodine radioisotopes; recurrence; prognosis
• Online Access: http://www.e-enm.org/upload/pdf/enm-2020-747.pdf
• ISSN: 2093-596X; 2093-5978

Background The clinical outcomes of delayed radioiodine remnant ablation (RRA) therapy in patients with low-risk papillary thyroid carcinoma (PTC) are unclear. We aimed to evaluate the clinical impact of the interval between total thyroidectomy (TT) and RRA therapy in patients with low-risk PTC. Methods We included 526 patients who underwent TT and RRA for low-risk PTC with a primary tumor size of >1 cm between 2000 and 2012. Patients were divided into the early (<90 days) and the delayed (≥90 days) RRA groups based on the interval between TT and RRA. The results of diagnostic whole-body scan (DxWBS), ongoing risk stratification (ORS; response to therapy), and disease-free survival (DFS) were evaluated before and after propensity score matching (PSM). Results Among the 526 patients, 75 (14.3%) patients underwent delayed RRA; they had more cervical lymph node metastasis and received a higher RRA dose than those who underwent early RRA. The median follow-up period was 9.1 years after initial therapy, and the structural recurrence rate was 1.9%. In DxWBS, 60 patients had focal iodine uptake limited in operative bed, with no significant difference between groups. According to ORS, 78%, 20%, 1%, and 1% patients were classified into excellent, indeterminate, biochemical incomplete, and structural incomplete response groups, respectively. There was no significant difference in ORS or DFS between groups before and after PSM. Conclusion The timing of the first RRA had no clinical impact in patients with low-risk PTC. Thus, the clinical decision for RRA can be determined >3 months after TT considering other prognostic factors.