Significance of Metastatic Lymph Node Ratio on Stimulated Thyroglobulin Levels in Papillary Thyroid Carcinoma after Prophylactic Unilateral Central Neck Dissection

Abstract

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 C3 central lymph nodes (CLNs) with C1 harboring metastasis. Of 129 specimens, 51 (39.5%) were eligible. CLNR was calculated as follows: (number of metastatic CLNs/number of CLNs retrieved) 9 100. 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 Conclusions. A higher CLNR was associated with a higher rate of postablative DsTg; this may imply higher future recurrence rate.Papillary thyroid carcinoma (PTC) is the most common type of differentiated thyroid carcinoma, and its ageadjusted incidence has doubled in the last 25 years. 1Despite its relatively good prognosis with a 10-year cancerspecific survival above 90%, locoregional recurrence is common.2 With recognition of the concept of stepwise progression of lymph node metastasis originating from the central (level VI) to the lateral compartment (levels II-V), a growing number of surgeons are advocating routine prophylactic central neck dissection (pCND) at the time of the total thyroidectomy for PTC.3 Although the role of pCND remains controversial because there is still no good evidence to show that it improves long-term outcomes such as cancer-specific or disease-free survival when compared to without pCND, the analysis of short-term markers for recurrence (e.g., postsurgical stimulated thyroglobulin level, sTg) seems to indicate that pCND may improve short-term outcomes. [4][5][6] Metastatic lymph node ratio (LNR) (defined as number of metastatic lymph nodes divided by number of lymph nodes examined) after prophylactic lymphadenectomy has been shown to be a promising prognostic variable in a variety of nonthyroidal primary cancers (e.g., colorectal, gastric, and pancreatic cancers). [7][8][9] The concept of LNR is based on the assumption that it indirectly reflects the extent 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, a...

Prognostic value of lymph node ratio in metastatic papillary thyroid carcinoma

“…After critical examination, nine studies were considered adequate according to the inclusion criteria. [18][19][20][21][22][23][24][25][26] These nine studies were published between 2012 and 2016. All studies were retrospective.…”

“…The patients' characteristics are summarised in Table I. A significant association was found between lymph node ratio and worse recurrence-free survival in 60 per cent and 75 per cent of the studies that investigated the effect of central compartment metastases 19 Lang et al 20 Schneider et al 21 Ryu et al 22 Chang et al…”

“…Five out of eight studies [19][20][21][22]24 investigated the effect of central compartment metastases (N 1a ) alone on recurrence. Three of the studies 19,21,22 (60 per cent) Lang et al 20 Schneider et al 21 Ryu et al 22 Chang et al…”

“…17 Multiple recent studies have evaluated the prognostic value of lymph node ratio in papillary thyroid carcinoma regarding loco-regional recurrence and survival, with varying results. [18][19][20][21][22][23][24][25][26] This study aimed to review recent publications addressing the prognostic value of lymph node ratio in metastatic papillary thyroid carcinoma.…”

“…[19][20][21][22][23][24][25][26] Different lymph node ratio thresholds were used in each study (range, 0.3-0.86). The prognostic values of lymph node ratio and the hazard ratios for loco-regional recurrence are presented in Table II.…”