Unilateral Multifocality Is Not a Risk Factor for Recurrence After Thyroid Lobectomy: A Study of 1,684 Patients With Differentiated Thyroid Cancer.

Abstract

Many studies indicate that multifocality is associated with high-risk features of differentiated thyroid cancer (DTC). Herein, we evaluated the impact of the unilateral multifocality on post-lobectomy recurrence in patients with DTC. We retrospectively analyzed 1,684 patients with DTC who underwent thyroid lobectomy from 2008 to 2015 using logistic regression models to calculate the relative risk on post-lobectomy recurrence. Tumor diameter increased from 4.9 mm to 8.1 mm and the proportion of extrathyroidal extension (ETE) and unilateral multifocality progressively increased from 2008 to 2015 (2.1% to 24.3% and 4.2% to 22.8%, respectively). During the 88.6-month follow-up period, 67 (3.98%) recurrences and 2 (0.12%) deaths were observed. There were 269 (16.0%) multifocal DTC cases. There was no significant difference between the multifocal and unifocal groups in terms of the proportion of recurrences (5.2% vs. 3.7%) and distant metastasis (0.4% vs. 0.1%). Logistic regression analysis revealed age <42.5 years (OR=1.83), tumor diameter greater than 7.5 mm (OR=1.89), and N1a (OR=2.04) were potent risk factors for post-lobectomy recurrence. Conversely, male sex (OR=0.77; p=0.407), ETE (OR=1.16; p=0.698) and multifocality (OR=1.23; p=0.526) were not risk factors for recurrence after thyroid lobectomy. A positive node ratio (PNR) ≥42.0%, N1a stage, a tumor diameter ≥7.5mm and age <42.5 years were significant risk factors for recurrence (Log-rank p=0.001, p=0.001, p=0.004 and p=0.009, respectively). Contrariwise, multifocality and ETE were proven to not be risk factors for DTC recurrence after thyroid lobectomy (Log-rank p=0.099 and p=0.126, respectively). Unilateral multifocality was not a risk factor for DTC recurrence after thyroid lobectomy and could not be considered an indication for immediate completion or total thyroidectomy.