Propensity Score Matched Outcome Analysis of Lobar Ablation Versus Completion Thyroidectomy in Low-Risk Differentiated Thyroid Cancer Patients: Median Follow-Up of 11 Years.

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Background: Radioactive iodine lobar ablation (RAILA) of the contralateral thyroid lobe has been suggested as an alternative to completion thyroidectomy in patients of differentiated thyroid cancer (DTC) who underwent initial hemithyroidectomy. However, data on long-term outcomes are scarce. In this study, we intended to describe the long-term outcomes of RAILA versus completion thyroidectomy in a cohort of low-risk DTC patients. Methods: Data of patients with low-risk DTC who underwent initial hemithyroidectomy, and were subsequently treated with either completion thyroidectomy or RAILA between 1996 and 2015, were collected and analyzed. The treatment outcomes included ablation rate, recurrence rate, recurrence-free survival (RFS), and adverse events, and were validated by propensity score matching analysis. Results: Of the 1243 patients (median age: 34 years, range: 5-78) with low-risk DTC, 514 patients underwent upfront RAILA while 729 patients underwent completion thyroidectomy followed by remnant ablation. The ablation rate following the first radioactive iodine (131I) cycle was 75.3% [95% confidence interval (CI) 71.3-78.9] in the RAILA group versus 84.1% [CI 81.2-86.6] in the completion thyroidectomy group (p < 0.001). Over median follow-up of 11.4 years (interquartile range: 8.3-15.8), the recurrence rates between the two groups were not significantly different (1.6% [CI 0.7-3.2] vs. 1.0% [CI 0.4-2.1], respectively, p = 0.343). The product limit estimate of RFS at 10 years was 98.6% [CI 97.6-99.6%] in the RAILA group versus 99.1% [CI 98.3-99.9%] in the completion thyroidectomy group (p = 0.391). The outcomes in 497 matched pairs generated through propensity score analysis were similar. None of the patients in the RAILA group experienced permanent hypocalcemia or recurrent laryngeal nerve palsy, while the corresponding rates in the completion thyroidectomy group were 10/729 (1.4%) (p = 0.006) and 5/729 (0.7%) (p = 0.080), respectively. Radiation thyroiditis was seen in 25/514 (4.9%) patients in the RAILA group versus 3/729 (0.4%) in the completion thyroidectomy group (p < 0.001). Conclusions: Upfront RAILA is seen to be a noninvasive, safe, and effective alternative to surgical completion thyroidectomy in low-risk DTC patients in the absence of macroscopic malignancy in the remaining thyroid lobe.