THU682 Long-term Outcomes Of Prophylactic Lateral Neck Dissection In Papillary Thyroid Carcinoma

Disclosure: A. Matsui: None. Y. Kuga: None. Y. Saito: None. K. Yoshioka: None. C. Masaki: None. J. Akaishi: None. K.Y. Hames: None. C. Tomoda: None. A. Suzuki: None. K. Matsuzu: None. W. Kitagawa: None. K. Sugino: None. K. Ito: None. Background: Prophylactic lateral neck dissection for papillary thyroid carcinoma is no longer recommended in guidelines of each country. Since 2010, it is not employed at our hospital as well. Thereafter, however, no long-term study has been conducted to investigate the differences in postoperative lymph node recurrence rate between patients who underwent prophylactic lateral neck dissection and those who did not; in this study, we have re-examined these differences. Object and Methods: There were 1732 cases of papillary thyroid carcinoma with no distant metastasis operated between January 2010 and December 2011. Among them, 1542 cases, excluding the cases with clinical lateral neck lymph node metastasis, were included in this study. Lymph node metastases were confirmed based on the diagnosis via cytological or histopathological examination. No exclusion criteria were established for the extent of thyroidectomy, and cases with lobectomy and total or subtotal thyroidectomy were included. Of the 1542 cases, 140 cases had lateral neck dissection (Group A) and 1402 cases did not have prophylactic lateral neck dissection (Group B), and both were compared. The study design was a retrospective study, comparing each group using the Kaplan-Meier method with lymph node recurrence as the endpoint. Results: Comparing the backgrounds of Group A and Group B, respectively, significant differences for age (49.2 years vs. 52.9 years, P = 0.003), macroscopic tumor invasion into the perithyroidal soft tissues (13 [9.3%] vs. 27 [1.9%], P < 0.001), and tumor size (24.8 mm vs. 13.1 mm, P < 0.001), were observed. And significant differences were observed in the 10-year postoperative lymph node recurrence-free rates (92.6% vs. 96.6%, P = 0.012) in Group A and Group B, respectively. When the backgrounds were matched by age, sex, macroscopic tumor invasion into the perithyroidal soft tissues, and tumor size using propensity score matching (138 matched pairs), no significant differences were observed in the 10-year recurrence-free rates (92.5% vs. 95. P = 0.208) in both groups. Conclusions: The results of this study showed no significant difference in postoperative lymph node recurrence rates between the two groups, suggesting that the presence or absence of prophylactic lateral neck dissection does not affect postoperative lymph node recurrence during the long-term observation period. Presentation: Thursday, June 15, 2023