Background: Prognostic significance of metastatic central lymph node ratio (CLNR) in papillary thyroid carcinoma (PTC) remains unknown. Because postsurgical detectable stimulated thyroglobulin (DsTg) after radioiodine ablation may imply persistent or recurrent disease, we evaluated the association between CLNR and rate of DsTg in patients with PTC who underwent unilateral prophylactic central neck dissection.
Methods: To be eligible for analysis, the prophylactic central neck dissection specimen had to contain ≥3 central lymph nodes (CLNs) with ≥1 harboring metastasis. Of 129 specimens, 51 (39.5%) were eligible. CLNR was calculated as follows: (number of metastatic CLNs/number of CLNs retrieved)×100. They were categorized into group 1 (CLNR<33.34%) (n=14), group 2 (CLNR 33.34-66.67%) (n=15), and group 3 (CLNR>66.67%) (n=22). Postablation sTg level was measured 6 months after radioiodine ablation. A multivariate analysis was conducted to identify factors for postablation DsTg.
Results: Young age, palpable neck swelling, large tumor size, advanced tumor, node, metastasis system (TNM) stage, and large number of metastatic CLNs were significantly associated with high CLNR (P<0.05). Compared to groups 1 and 2, group 3 had significantly higher DsTg rate (P=0.018). Those who developed subsequent recurrence had significantly higher DsTg rate than those who did not (100% vs. 39.1%, P=0.013). In the multivariate analysis for postablative DsTg, after adjusting for age, palpable neck swelling, tumor size, TNM stage, and number of metastatic CLNs, CLNR was the only independent factor (odds ratio 1.15, 95% confidence interval 1.01-1.31, P=0.036).
Conclusions: A higher CLNR was associated with a higher rate of postablative DsTg; this may imply higher future recurrence rate.