Endocrine Abstracts

Background: We evaluated the impact of the multifocality on post-lobectomy recurrence in patients with differentiated thyroid cancer (DTC).

Methods: We 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 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; 265 multifocal papillary thyroid cancer (PTC) and 4 collision tumors. There was no significant difference between the multifocal and unifocal groups in terms of the proportion of recurrences (5.2% vs. 3.7%, P = 0.262) and distant metastasis (0.4% vs. 0.1%). Logistic regression analysis revealed a positive nodal ratio (PNR) above 42.0% (OR=3.56) to be the unique and potent risk factor for DTC recurrence. Conversely, tumor diameter greater than 7.5 mm, age < 42.5 years, ETE, and multifocality were not risk factors. A PNR above 42.0% and N1a stage were potent risk factors on the Kaplan-Meier analysis. Tumor diameter greater than 7.5mm and age < 42.5 years were equally significant risk factors. 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: Multifocality is not a risk factor for DTC recurrence after thyroid lobectomy and should not be considered an indication for immediate completion or total thyroidectomy.