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

Background/aim: 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.

Patients And Methods: 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.

Results: 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).

Conclusion: 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.