Survival after hemithyroidectomy versus total thyroidectomy in non-high-risk differentiated thyroid cancer: population-based analysis

Background: The extent of thyroid surgery remains controversial for differentiated thyroid cancers (DTCs) that measure more than 1 cm but are not considered high risk. This study aimed to compare survival outcomes between hemithyroidectomy (HT) and total thyroidectomy (TT) in non-high-risk DTCs. Methods: A population-based retrospective cohort of patients with non-high-risk DTCs more than 1 cm undergoing HT or TT between 1997 and 2017 in a territory with 41 public hospitals and clinics serving a population of 7 million was analysed. Multivariable Cox proportional hazards regression models adjusted for patient demographics and clinical parameters were used to compare the overall, disease-specific, and recurrence-free survival between TT and HT. Risks of postoperative complications were compared between the two groups. Results: A total of 4771 patients (HT, 1368; TT, 3403) underwent thyroid surgery as a primary treatment. Median (range) follow-up was 117 (range: 72-179) months. Patients in the TT and HT groups had comparable risks of overall survival (HR 0.87; 95 per cent c.i. 0.73 to 1.04; P = 0.119) and disease-specific survival (HR 0.85; 95 per cent c.i. 0.52 to 1.40; P =0.518). The TT group had better recurrence-free survival (HR 0.37; 95 per cent c.i. 0.26 to 0.52; P < 0.001) than the HT group. The temporary and permanent hypoparathyroidism rates in TT group were 14.96 per cent and 7.49 per cent respectively; none were reported in the HT group. Conclusions: Despite the comparable overall and disease-specific survivals, TT was associated with better recurrence-free survival than HT in a 10-year follow-up. This was at the expense of higher surgical morbidity rate in TT.