(0686) Nationwide-Analysis of the Management and Survival of Noninvasive Follicular Thyroid Neoplasm With Papillary-Like Nuclear Features

Introduction: Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was classified in 2016 as a thyroid neoplasm with unique nuclear features and indolent behavior with the goal of reducing unnecessary treatment. In the subsequent period, this study aims to assess the clinicopathologic, treatment, and survival patterns in NIFTP compared to conventional papillary and follicular thyroid cancers.

Methods: Retrospective database study using the National Cancer Database (NCDB). The NCDB was queried for patients diagnosed with primary NIFTP, follicular thyroid cancer (FTC), or papillary thyroid cancer (PTC) from 2017 to 2021. Kaplan-Meier method was used to assess and compare 3-year overall survival (OS) rates. Clinicopathologic features and treatment patterns of patients were analyzed using a chi-squared test. Finally, COX multivariate regression was performed.

Results: In the study period, 4,632 patients were diagnosed with NIFTP, 8,201 with FTC, and 103,077 with PTC. NIFTP was more likely to present as a Stage I neoplasm (86.4%, p < 0.001) than FTC (64.2%) and PTC (82.3%), had the lowest rate of lymphovascular invasion (7.3%, p < 0.001), and the highest rate of negative margins (95.6%, p < 0.001). Patients with NIFTP underwent lobectomy at a higher rate (38%, p < 0.001) than other histologies, had the lowest rates of elective neck dissection (16%, p < 0.001), and lowest rates of adjuvant radioactive iodine treatment (17%, p < 0.001). At 3 years, OS was greater in NIFTP (97.7%) than both FTC (93.8%) and PTC (96.6%) (p < 0.001). On multivariate regression, there were no significant differences in survival. There were no differences in the management and survival of NIFTP tumors >4cm when compared to smaller tumors.

Conclusions: Our national hospital-based results support that NIFTP is an indolent thyroid neoplasm that has been treated less aggressively than its FTC and PTC counterparts with reassuring survival outcomes.