Prognostic implications of lymph node yield and lymph node ratio in papillary thyroid carcinoma

Predictors of treatment response in lymphogenic metastasized papillary thyroid cancer: a histopathological study

BACKGROUND

Lymph node metastases in papillary thyroid cancer (PTC) increase the risk for persistent and recurrent disease. Data on the predictive value of histopathological features of lymph node metastases, however, are inconsistent. The aim of this study was to evaluate the prognostic significance of known and new histopathological features of lymph node metastases in a well-defined cohort of PTC patients with clinically evident lymph node metastases.

METHODS

A total of 1042 lymph node metastases, derived from 129 PTC patients, were reexamined according to a predefined protocol and evaluated for diameter, extranodal extension, cystic changes, necrosis, calcifications, and the proportion of the lymph node taken up by tumor cells. Predictors for a failure to achieve a complete biochemical and structural response to treatment were determined.

RESULTS

The presence of more than 5 lymph node metastases was the only independent predictor for a failure to achieve a complete response to treatment (odds ratio [OR] 3.39 [95% CI, 1.57-7.33], P < .05). Diameter nor any of the other evaluated lymph node features were significantly associated with the response to treatment.

CONCLUSIONS

Detailed reexamination of lymph nodes revealed that only the presence of more than 5 lymph node metastases was an independent predictor of failure to achieve a complete response to treatment. No predictive value was found for other histopathological features, including the diameter of the lymph node metastases. These findings have the potential to improve risk stratification in patients with PTC and clinically evident lymph node metastases.

Prospective application of a prediction model for lateral lymph node metastasis in papillary thyroid cancer patients with central lymph node metastasis

Objective

This study aimed to develop and apply a prediction model to estimate the probability of lateral lymph node metastasis (LLNM) in patients with cN0 unilateral papillary thyroid carcinoma (PTC) with central lymph node metastasis (CLNM).

Setting

All study data were collected from a single tertiary hospital.

Methods

Univariable and multivariable logistic regression analyses were used to explore independent predictors of LLNM in the derivation and internal validation cohorts, which were used to construct and validate a nomogram. Another 96 patients were included prospectively to evaluate the efficacy of this nomogram.

Results

Maximum tumor diameter greater than 1.0 cm (OR, 2.712; 95% CI, 1.412-5.210), multifocality (OR, 2.758; 95% CI, 1.120-6.789), the number of CLNM ≥3 (OR, 2.579; 95% CI, 1.315-5.789), CLNM ratio ≥0.297 (OR, 2.905; 95% CI, 1.396-6.043), and tumors located in the upper portion (OR 2.846, 95% CI 1.151-7.039) were independent predictors associated with LLNM. The prediction model showed excellent discrimination with an AUC of 0.731 (95% CI, 0.635-0.827). Novel risk stratification for LLNM was constructed based on this nomogram. In the prospective cohort, we stratified these patients into three risk subgroups: low-, moderate-, and high-risk subgroups and we found that the probability of LLNM was positively correlated with the total points from the nomogram.

Conclusion

This nomogram was applied in prospective clinical practice and distinguished PTC patients with a genuinely high risk of LLNM. Surgeons can use our nomogram to tailor the surgical plan and to credibly determine further postoperative therapy.

Comparison of staging and recurrence predictors in patients with differentiated thyroid cancer between the 7th and 8th editions of the American Joint Committee on Cancer staging systems

BACKGROUND

The predictive value of American Joint Committee on Cancer (AJCC) 8 for recurrence in differentiated thyroid cancer (DTC) is not known. We aimed to compare AJCC 7 and 8 regarding the differences in staging and recurrence predictors in DTC.

METHODS

Demographic, clinical (duration of disease and follow-up, the extent of surgery), laboratory (TSH, fT4, thyroglobulin, and antithyroglobulin), pathological (type of thyroid cancer, localization, multifocality, diameter, extrathyroidal extension [ETE], and lymph node [LN] metastasis), and imaging findings (sonography, and whole-body scan), and follow-up features (metastases, recurrence and/or persistence, and RAI need) were retrospectively analyzed in adult patients with DTC followed-up for at least six months. Staging was determined in accordance with AJCC 7 and AJCC 8, prediction of recurrence and persistence by ATA risk stratification, and death risk by AMES systems. The alterations in staging and recurrence predictors were analyzed.

RESULTS

A majority of study patients (N.=524) were female (N.=424) and diagnosed with papillary cancer (N.=511), the median age at diagnosis was 44. 97.89% (N.=93) of stage 2-4 patients (N.=95) in AJCC 7 were down-staged in AJCC 8. We down-staged 41 patients of 45-55 years of age into stage 1 in AJCC 8 independent of LN status. A percentage of 26.71% of patients (N.=140) did have persistence, 9.54% (N.=50) persistence at the last follow-up, and 9.54% (N.=50) had recurrence. According to AJCC 8, T4 and AMES high risk were predictors for recurrence (hazard ratio: 3.053, P=0.023; hazard ratio:2.465, and P=0.005; respectively). Both AJCC 7 and 8 were associated with recurrence (P=0.008 and P<0.001, respectively). Stage 4 in AJCC 7, and stages 3 and 4 in AJCC 8 better predicted the probability of recurrence.

CONCLUSIONS

Our findings suggest that AJCC 8 better predicted the recurrence in DTC than AJCC 7. In AJCC 8, T4 tumor, AMES high risk, stages 3 and 4 predicted recurrence. The vast majority of patients with stages 2-4 in AJCC 7 were down-staged in AJCC 8.

The impact of lymph node ratio on disease recurrence in papillary thyroid microcarcinoma

INTRODUCTION

Lymph node (LN) metastases in papillary thyroid microcarcinomas (microPTCs) are common. The lymph node ratio (LNR) has been proposed as a risk factor for recurrence in papillary thyroid cancer. However, its relevance in microPTC is undetermined.

METHODS

Patients who underwent resection of their microPTC with concomitant LN clearance between 2005 and 2018 were identified. The LNR was calculated as the ratio of positive LNs to the total number of LNs.

RESULTS

Data on 50 patients (36 female [72%]; median age 47 years [range: 19-84]) who underwent LN clearance (28 central [56%] vs 22 central + lateral [44%]) were analysed. Positive LNs were found in over two-thirds of the patients (n = 34; 68%). After a median follow-up of 61 months, 14 patients (28%) had developed recurrence. Positive LNs were not found to impact recurrence-free survival; extranodal extension and an LNR ≥ 0.26 were found to significantly increase the risk of recurrence on unadjusted analyses (p < 0.05).

CONCLUSIONS

LN metastases are frequent among patients with microPTC. A higher LNR seems to be associated with recurrence. Additional studies are needed to further clarify these findings and to assess the possible role of LNR in treatment and surveillance.

Lymph Node Ratio Predicts Recurrence in Patients with Papillary Thyroid Carcinoma with Low Lymph Node Yield

The American Thyroid Association risk stratification system suggests that having >5 metastatic lymph nodes (LNs) increase the recurrence risk in patients with papillary thyroid carcinoma (PTC). However, little is known about PTC with <5 harvested LNs. This study aimed to stratify patients with low-LN-yield (low-LNY) PTC based on lymph node ratios (LNRs). From 2007 to 2017, 6317 patients who underwent thyroidectomies were diagnosed with PTC at Seoul St. Mary's Hospital, and 909 patients with low LNYs were included in the study. Tumor recurrence was compared based on LNR. The LNR cutoff was determined using a receiver operating characteristic curve. Forty-six patients (5.1%) experienced recurrences over a mean follow-up period of 127.24 ± 33.6 months (range, 5-190 months). The cutoff for the low-LNR (n = 675) and high-LNR (n = 234) groups was 0.29 (AUC = 0.676, 95% CI = 0.591-0.761, p < 0.001). The recurrence rate was significantly higher in the high-LNR group compared to the rate in the low-LNR group (12.4% vs. 2.5%, p < 0.001). Multivariate analysis using Cox regression revealed that tumor size and LNR ≥ 0.29 were independent prognostic factors for recurrence. Therefore, LNR can be utilized to stratify the risk of recurrence in patients with low-LNY PTC.

Optimal value of lymph node ratio and metastatic lymph node size to predict risk of recurrence in pediatric thyroid cancer with lateral neck metastasis

BACKGROUND

No specific guideline exists for risk stratification based on lymph node (LN) status in pediatric thyroid cancer. The purpose of our study is to identify optimal values of lymph node ratio (LNR) and largest metastatic LN size for predicting recurrent/persistent disease, especially in children with lateral neck metastasis (N1b).

METHODS

We conducted a retrospective study from January 1997 to June 2018 at Samsung Medical Center. A total of 50 papillary thyroid carcinoma (PTC) patients who underwent total thyroidectomy + both central neck dissection (CND) + modified radical neck dissection (MRND) (unilateral or bilateral) was enrolled.

RESULTS

The median follow-up duration was 60.8 months (range, 6.2-247 months). The mean age was 14.6 years, and the mean tumor size was 2.9 cm. Mean size of the largest metastatic LN was 1.5 cm. Mean value of central LNR was 0.6, and mean value of lateral LNR was 0.3. Largest metastatic LN size [HR = 2.0 (95% CI 1.0-4.0), p = 0.040] and lateral LNR [HR = 43.6 (95% CI 2.2-871.0), p = 0.014] were significant prognostic factors for recurrence. The optimal combination of lateral LNR and largest metastatic LN size to predict recurrence were 0.3 and 2.5 cm, respectively, with the largest AUC (AUC at 60 months = 77.4) and significant p-value (p = 0.009 and p = 0.021) (Table 3). Kaplan-Meier curves showed significant differences in recurrence-free survival (RFS) rates among four groups (Fig. 2A,2B).

CONCLUSIONS

In pediatric PTC patients with N1b, lateral LNR and largest metastatic LN size are significant predictors for recurrence. Children with lateral LNR > 0.3 or any metastatic lymph node > 2.5 cm in the largest dimension have higher risk for recurrence. Children are classified as extensive N1b if lateral LNR > 0.3 or pathologic N1 with largest LN size > 2.5 cm, and vice versa.

Clinical Significance of the Lymph Node Ratio of the Second Operation to Predict Re-Recurrence in Thyroid Carcinoma

The purpose of this study was to establish the risk factors for re-recurrences and disease-specific mortality (DSM) in recurrent thyroid cancer. Patients with recurrent thyroid cancer who underwent initial thyroid surgery from January 2000 to December 2019 at Seoul St. Mary's Hospital (Seoul, Korea) were assessed. Clinicopathological characteristics and long-term oncologic outcomes were compared between patients with one recurrence (n = 202) and patients with re-recurrences (n = 44). Logistic regression and cox-regression analyses were conducted to determine the risk factors for re-recurrences and DSM, respectively. Receiver-operating characteristic curve analysis was performed to determine the cutoff value for lymph node ratio (LNR) as a predictor of re-recurrences. DSM was significantly higher in the re-recurrence group compared with the single-recurrence group (6.8% vs. 0.5%, p = 0.019). Surgical treatment at the first recurrence significantly lowered the risk of re-recurrences. Age (≥55), male sex, and LNR (≥0.15) were independent significant risk factors for re-recurrences in patients who underwent surgery at the first recurrence. Surgical resection is the optimal treatment for initial thyroid cancer recurrence. LNR at re-operation is more effective in predicting re-recurrence than the absolute number of metastatic LNs.

Recurrence Risk Evaluation in Patients with Papillary Thyroid Carcinoma: Multicenter Machine Learning Evaluation of Lymph Node Variables

Background: Lymph node (LN)-related risk factors have been updated to predict long-term outcomes in patients with papillary thyroid carcinoma (PTC). However, those factors’ analytic appropriateness and general applicability must be validated. This study aimed to assess LN-related risk factors, and suggest new LN-related risk categories. Methods: This multicenter observational cohort study included 1232 patients with PTC with N1 disease treated with a total thyroidectomy and neck dissection followed by radioactive iodine remnant ablation. Results: The median follow-up duration was 117 months. In the follow-up period, structural recurrence occurred in 225 patients (18.3%). Among LN-related variables, the presence of extranodal extension (p < 0.001), the maximal diameter of metastatic LN foci (p = 0.029), the number of retrieved LNs (p = 0.003), the number of metastatic LNs (p = 0.003), and the metastatic LN ratio (p < 0.001) were independent risk factors for structural recurrence. Since these factors showed a nonlinear association with the hazard ratio of recurrence-free survival (RFS) rates, we calculated their optimal cutoff values using the K-means clustering algorithm, selecting 0.2 cm and 1.1 cm for the maximal diameter of metastatic LN foci, 4 and 13 for the number of metastatic LN, and 0.28 and 0.58 for the metastatic LN ratio. The RFS curves of each subgroup classified by these newly determined cutoff values showed significant differences (p < 0.001). Each LN risk group also showed significantly different RFS rates from the others (p < 0.001). Conclusions: In PTC patients with an N1 classification, our novel LN-related risk estimates may help predict long-term outcomes and design postoperative management and follow-up strategies. After further validation studies based on independent datasets, these risk categories might be considered when redefining risk stratification or staging systems.

A novel prognostic model based on log odds of positive lymph nodes to predict outcomes of patients with anaplastic thyroid carcinoma after surgery

OBJECTIVE

The eighth version of the American Joint Committee on Cancer (8th AJCC) system for anaplastic thyroid carcinoma (ATC) added lymph node (LN) metastasis as the staging element. This study aimed to explore the association between LN status and ATC's prognosis, identify the optimal LN index and establish a novel prognostic model.

DESIGN AND PATIENTS

Data of 199 ATC patients after surgery were collected from the Surveillance, Epidemiology and End Results (SEER) database, then randomly divided into training and validation cohorts.

MEASUREMENTS

We compared the prognostic value of AJCC N status, number of positive LN (PLNN), ratio of LN (LNR) and log odds of positive LN (LODDS). We conducted univariate and multivariate Cox analyses to determine the independent prognostic factors for ATC, and constructed a novel prognostic model. The concordance index (C-index), area under the receiver-operating characteristic curve (AUC), calibration curves and decision curve analysis (DCA) were used to assess the nomogram's predictive performance.

RESULTS

LODDS showed the highest accuracy among four LN systems to predict overall survival (OS) for ATC. In the training cohort, the C-index of the LODDS-based nomogram was 0.738. The AUCs were 0.813, 0.850 and 0.869 for predicting 1-, 2- and 3-year OS, respectively. The calibration plots and DCA indicated the great clinical applicability of the model. The above results were verified in the validation cohort.

CONCLUSIONS

LODDS showed better predictive performance than other LN schemes in ATC. The LODDS-incorporated nomogram has the potential to more precisely predict the prognosis for ATC patients than the AJCC system.

Lymph node ratio in lateral neck is an independent risk factor for recurrence-free survival in papillary thyroid cancer patients with positive lymph nodes

BACKGROUND

The purpose of this study was to explore the impact of the lymph node ratio on prognosis in papillary thyroid cancer patients with lymph node metastasis.

METHODS

Data from papillary thyroid cancer patients with positive nodes who were initially treated at our institution during 2015-2016 were analysed. Univariate and multivariate Cox proportional hazard models were adopted to predict prognostic factors. A receiver operating characteristic (ROC) curve was used to find the best cut-off value of the lymph node ratio (LNR). Kaplan-Meier curves were used to show the relationship between the LNR in the lateral neck and recurrence-free survival.

RESULTS

The median follow-up time was 64.6 months, and recurrence occurred in 16 of 662 patients (2.27%). Univariate analysis showed that male sex, primary tumour size (&gt;17 mm), visible extrathyroidal extension, LNR in the central neck (&gt;0.5), LNR in the lateral neck (&gt;0.10), and visible extranodal extension were significantly correlated with recurrence-free survival (RFS) (p &lt; 0.05). Multivariate analysis using the Cox proportional hazards model showed that the LNR in the lateral neck was an independent risk factor for RFS (p = 0.039; HR 14.76).

CONCLUSION

The LNR in the lateral neck was an independent risk factor for recurrence-free survival. For patients with a high lymph node ratio in the lateral neck, more frequent follow-up might be needed.

Nomograms based on sonographic and clinicopathological characteristics to predict lateral lymph node metastasis in classic papillary thyroid carcinoma

BACKGROUND

Lateral lymph node metastasis (LLNM) has been considered a risk factor of recurrence in papillary thyroid cancer (PTC). Preoperative detecting LLNM accurately is difficult. Solitary lateral lymph node metastasis is a special type of LLNM. We aimed to develop nomograms for predicting LLNM and multiple lateral lymph node metastasis (MLLNM).

METHODS

We retrospectively retrieved 528 classic PTC patients that underwent surgery between March 2019 and May 2020. Sonographic and clinicopathological features were collected. Risk factors of LLNM and MLLNM were determined by univariate and multivariate analysis. Nomograms for predicting LLNM and MLLNM were developed.

RESULTS

LLNM was independently associated with tumor size, the number of foci, location, margin, central lymph node metastasis, and lymph node ratio. Independent predictors of MLLNM were age, margin, and the number of metastatic lymph nodes in central compartment. By using above variables, we constructed nomograms for predicting LLNM and MLLNM, with area under curves of 0.864 and 0.748, respectively.

CONCLUSION

Through these accurate and easy-to-use nomograms, we can detect the risk of residual LLNM postoperatively for classic PTC patients who did not receive lateral neck dissection and provide an individualized plan for postoperative management of classic PTC patients.

How Many Nodes to Take? Lymph Node Ratio Below 1/3 Reduces Papillary Thyroid Cancer Nodal Recurrence

INTRODUCTION

Papillary thyroid carcinoma (PTC) accounts for the majority of thyroid malignancies; risk of PTC recurrence over a 30-year period is approximately 30%, of which 70% occur as nodal metastases. Patients with nodal disease who are treated with therapeutic dissection are at higher risk for recurrence, but optimal nodal yield has not been defined. We aim to determine variables predictive of nodal recurrence of PTC within the first 5 years of surgery, with a focus on lymph node ratio (LNR), to inform clinical decision-making.

METHODS

Retrospective chart review identified 41 patients with nodal recurrence of PTC and 284 without nodal recurrence following thyroid surgery from 2000 to 2015. Cohorts were compared with regards to clinical history, surgical findings, and tumor characteristics.

RESULTS

The fraction of the patients who underwent therapeutic central or lateral lymph node dissection was significantly higher in the nodal recurrence cohort. Maximum tumor size, presence of extrathyroidal extension, largest lymph node focus, LNR, postoperative thyroglobulin level, and administration of postoperative radioactive iodine were significantly increased in the PTC nodal recurrence group. LNR greater than 0.3 held the highest level of significance as a binary cutoff and captured the larger proportion of patients in the nodal recurrence cohort (68.3%).

CONCLUSION

This study demonstrates characteristics to help assess risk of nodal recurrence of PTC and suggests LNR of lower than 0.3 is optimal to reduce risk of recurrence. The next steps include cohort studies to validate findings and weight variable analysis to optimize the extent of surgical therapeutic dissection.

LEVEL OF EVIDENCE

4 Laryngoscope, 132:1883-1887, 2022.

Clinical assessment of T2 papillary thyroid carcinoma: a retrospective study conducted at a single tertiary institution

The extent of surgery among patients with T2 papillary thyroid carcinoma (PTC) remains controversial. Thus, we herein aimed to evaluate the risk factors for recurrence, particularly based on the extent of surgery, among patients with T2 PTC at a single tertiary institution. We assessed 251 patients who underwent thyroid surgery for T2 PTC from January 2009 to December 2014 at Seoul St. Mary's Hospital (Seoul, Korea). The mean follow-up duration was 100.7 months. Eleven (4.4%) patients had recurrence. The recurrence rates did not significantly differ in terms of the extent of surgery (p = 0.868). Patients with a high lymph node ratio (LNR) had a significantly higher recurrence rate than those with a low LNR (p < 0.001). According to a recurrence pattern analysis, five of six patients in the lobectomy group had recurrence in the ipsilateral lateral compartment. A multivariate analysis revealed that a high LNR was a significant risk factor for recurrence (hazard ratio: 11.025, p = 0.002). Our results suggest that patients without clinical evidence of any lymph node metastases and those with limited lesions in the thyroid gland can undergo lobectomy and LNR can serve as an independent risk factor for predicting recurrence in T2 PTC.

Lymph Node Metastases Identified at the Post-Ablation 131I SPECT/CT Scan Is a Prognostic Factor of Intermediate-Risk Papillary Thyroid Cancer

The intermediate-risk category of papillary thyroid cancer (PTC) comprises heterogeneous patients within a wide range of stages and varied care management. Understanding the risk features of recurrence observed after the initial therapy should be emphasized. We aimed to evaluate the prognostic significance of radioactive iodine-avid lymph nodes observed during the initial treatment of patients with PTC that were considered to be at intermediate risk. Data on patients with intermediate-risk PTC treated from 2012 to 2018 were retrospectively reviewed. Post-therapeutic SPECT/CT (Rx SPECT/CT) was evaluated in the enrolled patients. The clinical, pathologic, and incidence of radioiodine-avid (RAI-avid) lymph node metastasis (mLN) on Rx SPECT/CT were reviewed, and risk factors related to recurrent disease were analyzed. After a median follow-up of 37.26 (30.90, 46.33) months, structural persistent/recurrent disease was detected in 9.81% (36/367) of patients with intermediate-risk tumors. The incidence of recurrence was higher in patients who demonstrated RAI-avid mLN after the initial therapy than in those who did not (p < 0.001). In a multivariate Cox proportional hazard regression analysis, RAI-avid mLN appeared to be a robust risk factor for recurrent disease after the initial therapy (HR: 8.967, 95% CI: 3.433−23.421, p = 0.000). RAI-avid mLN is a significant risk factor for recurrent intermediate-risk PTC after the initial treatment.

Lymph node ratio is superior to AJCC N stage for predicting recurrence in papillary thyroid carcinoma

OBJECTIVE

Recently, lymph node ratio (LNR) has emerged as an alternative to American Joint Committee on Cancer (AJCC) N stage, with superior prognostic value. The utility of LNR in Middle Eastern papillary thyroid carcinoma (PTC) remains unknown. Therefore, we retrospectively analyzed a large cohort of 1407 PTC patients for clinicopathological associations of LNR.

METHODS

Receiver operating characteristics (ROC) curve was used to determine the cut-off for LNR. We also performed multivariate logistic regression analysis to determine whether LNR or AJCC N stage was superior in predicting recurrence in PTC.

RESULTS

Based on ROC curve analysis, a cut-off of 0.15 was chosen for LNR. High LNR was significantly associated with adverse clinicopathological characteristics such as male sex, extrathyroidal extension, lymphovascular invasion, multifocality, bilateral tumors, T4 tumors, lateral lymph node (N1b) involvement, distant metastasis, advanced tumor stage, American Thyroid Association (ATA) high-risk category and tumor recurrence. On multivariate analysis, we found that LNR was a better predictor of tumor recurrence than AJCC N stage (odds ratio: 1.96 vs 1.30; P value: 0.0184 vs 0.3831). We also found that LNR combined with TNM stage and ATA risk category improved the prediction of recurrence-free survival, compared to TNM stage or ATA risk category alone.

CONCLUSIONS

The present study suggests LNR is an independent predictor of recurrence in Middle Eastern PTC. Integration of LNR with 8th edition AJCC TNM staging system and ATA risk stratification will improve the accuracy to predict recurrence in Middle Eastern PTC and help in tailoring treatment and surveillance strategies in these patients.

The effect of intraoperative neuromonitoring on the number of lymph nodes excised and recurrence when applied during neck dissection in cases of papillary thyroid cancer

Purpose

The aim of this study was to evaluate the effect of neuromonitoring on the number of lymph nodes (LNs) removed when applied during neck dissection.

Methods

A total of 166 patients receiving neck dissection due to papillary thyroid cancer were separated into 2 groups (monitoring group, n = 76; non-monitoring group, n = 90).

Results

The number of LNs dissected was observed to be statistically significantly higher in the monitoring group (P = 0.001), and the difference between the groups in the number of positive LNs was significant (P = 0.031). There was seen to be a negative relationship between the number of positive LNs dissected and recurrence (r = –0.404, P = 0.005).

Conclusion

Intraoperative neuromonitoring during neck dissection makes a positive contribution to the prevention of the development of recurrence by increasing the number of LNs excised and the number of metastatic LNs.

Risk probability model for residual metastatic lymph node in patients with papillary thyroid microcarcinoma undergoing cervical central lymph node dissection

To establish a risk probability model for residual metastatic lymph nodes in patients with papillary thyroid microcarcinoma (PTMC) after cervical central lymph node dissection (CLND). The clinical data of patients with PTMC treated in the First Affiliated Hospital of Kunming Medical University from 2007 to 2020 were retrospectively reviewed. All patients underwent thyroidectomy with CLND, and at least one lymph node was examined. Based on the distribution characteristics of metastatic lymph nodes from this retrospective cohort, a probabilistic model for the risk of residual metastatic lymph node was established. β-Binomial distribution was used to estimate the probability of residual metastatic lymph node as a function of the number of lymph nodes examined. Among 5399 patients included in the probabilistic model, central lymph node metastases were observed in 1664 cases (30.8%). After model correction, the real lymph node metastasis rate increased from 30.8% to 38.9%. The probability of false negative of central lymph node was estimated to be 31.3% for patients with a single node examined, while decreased to 10.0% and 4.9% when 7 and 12 nodes were examined, respectively. In the sensitivity analysis limited to patients with or without Hashimoto thyroiditis, the performance of probability model was also satisfactory. The established risk probability model in this study quantifies the risk of residual metastatic lymph nodes after CLND in patients with PTMC, which can be used as complementary indicators for the risk of recurrence/persistence disease at postoperative evaluation. The study also provides a new method to evaluate the impact of residual metastatic lymph nodes on the prognosis of tumor patients through retrospective data.

Clinical impact of radioactive iodine dose selection based on the number of metastatic lymph nodes in patients with papillary thyroid carcinoma: A multicenter retrospective cohort study

OBJECTIVE

The aim of this study is to investigate whether the number of metastatic lymph nodes (LNs) could be used as a basis in the radioactive iodine (RAI) dose selection for patients with papillary thyroid carcinoma (PTC).

PATIENTS

A total of 595 patients with PTC who received first RAI therapy after total or near-total thyroidectomy and had no evidence of disease in treatment response assessment were retrospectively enroled from five hospitals. The patients were classified into two subgroups based on the number of metastatic LNs (>5). The multivariate Cox-proportional hazard model was performed to identify the significant factors for recurrence prediction in each group as well as all enroled patients.

RESULTS

Overall, 22 (3.7%) out of 595 patients had the recurrent disease during the follow-up period. The number of metastatic LNs (>5) was only a significant factor for recurrence prediction in all enroled patients (odds ratio: 7.834, p < .001). In the subgroup with ≤5 metastatic LNs, the presence of extrathyroidal extension was only associated with recurrence (odds ratio: 7.333, p = .024) in multivariate analysis. RAI dose was significantly associated with recurrence rate in which the patients with high-dose RAI (3.7 GBq or higher) had less incidence of recurrence than those with low-dose RAI (1.11 GBq) in the subgroup with more than five metastatic LNs (odds ratio: 6.533, p = .026).

CONCLUSIONS

High-dose RAI (≥3.7 GBq) therapy significantly lowered the recurrence rate in patients with more than five metastatic LNs. Therefore, RAI dose should be determined based on the number of metastatic LNs as well as conventional risk factors.

Lymph node yield in the initial central neck dissection (CND) associated with the risk of recurrence in papillary thyroid cancer: A reoperative CND cohort study

BACKGROUND

To evaluate the relationship between lymph node yield (LNY) from the initial central neck dissection (CND) and the risk of recurrence in patients undergoing reoperative CND for papillary thyroid cancer (PTC).

METHOD

We reviewed clinical data from all patients with pathologically proven PTC who underwent central neck and/or lateral neck dissection reoperations at Nanfang Hospital between 2012 and 2020. Patient demographics, tumor characteristics, clinical data and follow-up information were obtained. In the initial CND, the total number of lymph nodes removed (LNY), total positive nodes removed, and the percentage of positive lymph nodes to the number of lymph nodes removed (PLN%) were determined.

RESULTS

A total of 162 patients were included in the study, with a median follow-up of 44 months. 62 had central neck disease recurrence. The optimal LNY and PLN% cut-off values for recurrence were 11 and 65%, respectively. Group 2 (LNY ≥ 11, PLN% < 65%) showed a significantly higher RFS rate than group 1 (LNY < 11 and PLN% < 65%; P < 0.001), group 3 (LNY < 11, PLN% ≥ 65%; P < 0.001), and group 4 (LNY ≥ 11, PLN% ≥ 65%; P = 0.038). Furthermore, group 4 had a higher RFS rate than group 1 (P = 0.008) and group 3 (P = 0.001). Multivariate analysis revealed that LNY < 11 in the central neck was an independent risk factor for recurrence/persistence in the initial surgery (P < 0.001).

CONCLUSION

Higher LNY in central and neck dissections is associated with lower papillary thyroid cancer recurrence rates, which was confirmed by a reoperative CND procedure. To minimize the risk of recurrence and the need for secondary therapy, surgeons should perform compartment-oriented CNDs when indicated.

Predictive Impact of Metastatic Lymph Node Burden on Distant Metastasis Across Papillary Thyroid Cancer Variants

Background: While numerous factors determine prognosis in papillary thyroid carcinoma (PTC), distant metastasis (M1) represents one of the most dire. Escalating nodal burden and aggressive histology may contribute to higher metastatic risk, but this relationship is poorly defined and challenging to anticipate. We evaluate the predictive impact of these histological features on predicting distant metastases at initial presentation. Methods: Univariate and multivariable logistic regression models of conventional and aggressive thyroid cancer variants (well-differentiated papillary thyroid carcinoma [WDPTC], diffuse sclerosing variant [DSV], tall cell variant [TCV], poorly differentiated thyroid cancer [PDTC], and anaplastic thyroid carcinoma [ATC]) identified via U.S. cancer registry data were constructed to determine associations between M1 status and quantitative nodal burden. Associations between metastatic lymph node (LN) number and M1 disease were modeled using univariate and multivariable logistic regression with interaction terms, as well as a linear continuous probability model. Results: Overall, M1 prevalence at disease presentation was 3.6% (n = 1717). When stratified by subtype, M1 prevalence varied significantly by histology (WDPTC [1.0%], DSV [2.3%], TCV [4.1%], PDTC [17.4%], ATC [38.4%] [p < 0.001]). For WDPTC, M1 prevalence escalated with metastatic LN number (0 LN+ [0.5%], 1-5 LN+ [2.0%], 6-10 LN+ [3.4%], >10 LN+ [5.5%] [p < 0.001]) and LN ratio (p < 0.001). A statistically significant interaction was observed between histology and increasing nodal burden for M1 risk. On multivariable analysis, each successive metastatic LN conferred increased M1 risk for WDPTC (odds ratio [OR] 1.06 [1.05-1.08], p < 0.001) and TCVs (OR 1.04 [1.02-1.07], p < 0.001). In contrast, other aggressive variants had a higher baseline M1 risk, but this did not vary based on the number of positive LN (DSV, OR 1.02 [0.95-1.10], p = 0.52; PDTC, OR 1.00 [0.98-1.02], p = 0.66; ATC, 1.00 [0.98-1.02], p = 0.97). Conclusions: Progressive nodal burden independently escalates the risk of distant metastasis in WDPTC and TCVs of PTC. Conversely, aggressive variants such as PDTC and ATC have substantial M1 risk at baseline and appear to be minimally affected by metastatic nodal burden. Consideration of these factors after surgery may help tailor clinical decision-making for treatment and surveillance. Further studies are warranted to calibrate the ideal management approach for these higher risk patient groups.

Prognostic value of lymph node ratio in children and adolescents with papillary thyroid cancer

OBJECTIVE

Neck lymph node (LN) metastasis is a common feature of paediatric papillary thyroid cancer, and LN ratio (LNR) is defined as the ratio of the number of positive LNs excised to the total number of removed. Unlike in adults, few data are available regarding the clinical implication of LNR in the paediatric population. Our purpose was to investigate the association of LNR with clinical outcomes in paediatric papillary thyroid cancer.

DESIGN & METHODS

The study retrospectively reviewed 136 consecutive children and adolescents with papillary thyroid cancer and LN involvement but no initial distant metastasis. Initial treatment, included in all patients a total thyroidectomy with central and/or lateral neck dissection followed by radioactive iodine ablation. Within the neck dissections, total number of LNs removed, total positive LNs and LN ratios were determined. The effect of clinicopathologic characteristics and intraoperative findings on persistent and recurrent diseases were analysed by univariate and multivariate analyses.

RESULTS

Median number of positive LNs was 9, and median LNR was 0.4. During a median follow-up of 49 months (range, 12.0-139 months), persistent disease occurred in 43 (31.6%) patients. The multivariable analysis showed that age and LNR were the independent factors predictive of persistent disease. Patients with a LNR >0.34 exhibited a threefold higher risk of persistent disease after initial therapy than the counterparts (P = .02).

CONCLUSION

Our findings suggest that LNR was an independent determinant predictive of persistent disease after initial therapy in children and adolescents with papillary thyroid cancer.

A prediction model incorporating the BRAFV600E protein status for determining the risk of cervical lateral lymph node metastasis in papillary thyroid cancer patients with central lymph node metastasis

BACKGROUND AND OBJECTIVES

Cervical lateral lymph node metastasis (LLNM) is a predictor of poor prognosis for papillary thyroid carcinoma (PTC) patients. However, the risk factors for LLNM remain unclear. The purpose of the study was to examine the risk factors for LLNM and construct a prediction model.

METHODS

With Ethics Committee approval, a total of 1198 PTC patients were retrospectively included in our study. Univariate and multivariate analyses were performed to explore the relationship between clinicopathological characteristics and LLNM. A nomogram for predicting LLNM in PTC patients with central lymph node metastasis (CLNM) was constructed and validated.

RESULTS

The negative BRAF^V600E protein expression was significantly correlated with positive LLNM status in PTC patients. In PTC patients with CLNM, the number of metastatic central lymph nodes (LNN) ≥ 3 and the ratio of metastatic central lymph nodes (LNR) ≥ 0.565 were found to be significantly associated with positive LLNM status. The nomogram for predicting LLNM risk in PTC patients with CLNM incorporated four risk factors: tumor size, the BRAF^V600E protein expression, LNN and LNR. The prediction model showed excellent discrimination, with a C-index of 0.714.

CONCLUSIONS

The negative BRAF^V600E protein expression was more likely to lead to LLNM. LNN ≥3 and LNR ≥0.565 were associated with LLNM risk in PTC patients with CLNM. Our nomogram might assist clinicians in developing individual suitable follow-up strategies for PTC patients with CLNM.

Value of Pyruvate Carboxylase in Thyroid Fine-Needle Aspiration Wash-Out Fluid for Predicting Papillary Thyroid Cancer Lymph Node Metastasis

The incidence of papillary thyroid carcinoma (PTC) is increasing. Lymph node metastatic status of PTC is a major factor for decision marking of surgery and surgical extend, however, no reliable tool exists for prediction of PTC nodal metastasis, for example, ultrasound cannot qualitatively diagnose and effectively detect central lymph node metastasis (CLNM). Therefore, the development of a new diagnostic biomarker is crucial for CLNM. Metabolic dysregulation is an important factor associated with malignancy and metastasis of tumors. Pyruvate carboxylase (PC) is a major anaplerotic enzyme that catalyzes the carboxylation of pyruvate to form oxaloacetate, which has been suggested to be involved in the tumorigenesis of several cancers, including PTC. This study aimed to explore the role of PC expression in thyroid fine-needle aspiration (FNA) wash-out fluid for predicting CLNM in PTC, and to explore how PC is involved in PTC development. The expression levels of PC in PTC tissues and normal thyroid tissues were first compared based on bioinformatics analysis of public databases, including the Gene Expression Profiling (GEPIA), Oncomine and Gene Expression Omnibus (GEO) databases. Then, the PC mRNA and protein expression levels were measured by RT-PCR and Immunohistochemistry (IHC) in surgical tissues from a total of 42 patients with surgically confirmed PTC, and compared in patients with and without CLNM. Further, to assess PC expression in diagnostic biopsies, a total of 71 thyroid nodule patients with ultrasound-guided FNA wash-out fluid samples and cytological diagnosis were prospectively enrolled in the study. Then, we analyzed the mechanism of PC-mediated PTC progression in vitro. This study showed that PC expression was higher in PTC tissues and thyroid FNA wash-out fluid samples from patients with CLNM than those from patients without CLNM, and that PC-induced PTC metastasis may occur through the TGF-β/Smad-regulated epithelial-mesenchymal transition (EMT) pathway.

Combined role of lymph node ratio and serum thyroglobulin levels in predicting prognosis of papillary thyroid carcinoma

OBJECTIVES

The aim of this study was to evaluate a prognostic value of the extent of metastatic lymph node combined with TSH-stimulated serum thyroglobulin (sTg) measured just before radioactive iodine (RAI) therapy in patients with papillary thyroid cancer (PTC).

METHODS

The retrospective study included 468 patients with PTC who underwent total thyroidectomy with neck dissection and postoperative RAI therapy. The extent of metastatic lymph node was evaluated with the lymph node ratio (LNR) which was defined as the number of metastatic lymph nodes out of the number of total removed lymph nodes. We investigated which factors could significantly predict persistent or recurrent disease (PRD).

RESULTS

LNR ≥0.4 (P = 0.002) and sTg ≥6.0 ng/mL (P < 0.001) were associated with PRD in univariate analysis. In multivariate analysis, only male [hazard ratio: 2.35, 95% confidence interval (CI): 1.18-4.66, P = 0.014] and sTg (hazard ratio: 9.35, 95% CI: 4.44-19.67, P < 0.001) were associated with PRD prediction. When we divided patients into two groups (patients with sTg level < 6.0 ng/mL and those with sTg level ≥ 6.0 ng/mL), LNR (≥0.4) was a significant predictor of PRD in patients with sTg <6.0 ng/mL (hazard ratio: 4.38, 95% CI: 1.22-15.72, P = 0.024).

CONCLUSIONS

LNR ≥0.4 was a significant predictor of PRD when the sTg level was <6.0 ng/mL. LNR should be used in combination with a relatively low level of serum sTg to predict the prognosis of patients with PTC.

A Stepwise Approach Using Metastatic Lymph Node Ratio-Combined Thyroglobulin for Customization of [18F]FDG-PET/CT Indication to Detect Persistent Disease in Patients with Papillary Thyroid Cancer

We investigated whether an indication for [¹⁸F]FDG-PET/CT to detect FDG-avid persistent disease (PD) could be identified precisely using the extent of metastatic lymph nodes (MLNs) and serum thyroglobulin (Tg) in papillary thyroid cancer (PTC) patients. This retrospective study included 429 PTC patients who underwent surgery and radioactive iodine (RAI) therapy. [¹⁸F]FDG-PET/CT and serum Tg were evaluated just before RAI therapy. The MLN ratio (LNR) was defined as the ratio of the number of MLNs to the number of removed LNs. To derive the LNR-combined criteria, different Tg cut-off values for identifying the PET/CT-indicated group for PD detection were applied individually to subgroups initially classified based on LNR cut-off values. The cut-off values for serum Tg, the number of MLNs, and LNR for a PET/CT indication were 6.0 ng/mL, 5, and 0.51, respectively. Compared to a single parameter (serum Tg, total number of MLNs, and LNR), the LNR-combined criteria showed significantly superior diagnostic performance in detecting FDG-avid PD (p < 0.001). The diagnostic performance of PET/CT in detecting FDG-avid PD was significantly improved when the PET/CT-indicated group was identified through the LNR-combined criteria in a stepwise manner; this can contribute to a customized PET/CT indication in PTC patients.

The Clinical Significance of Lymph Node Ratio and Ki-67 Expression in Papillary Thyroid Cancer

BACKGROUND

The N stage in papillary thyroid cancer (PTC) is an important prognostic factor based on anatomical localization of cervical lymph nodes (LNs) only and not the extent of lymphatic metastasis. In this retrospective study, the clinical significance of lymph node ratio (LNR) and tumor cell proliferation in relation to the conventional classification of PTC was explored.

METHODS

Patients diagnosed with PTC at the Karolinska University Hospital in Stockholm, Sweden, during the years 2009-2011 were included. The LNR, defined as the number of metastatic LNs divided by the total number of LNs investigated, and the Ki-67 index were analyzed in relation to clinical data.

RESULTS

The median number of LN removed was 16 with the following N stage distribution: N0 (26%), N1a (45%), and N1b (29%). A Ki-67 index of ≥3% was significantly correlated with the presence of metastases and tumor recurrence with a sensitivity of 50% and specificity of 80% (p = 0.015). Lymph node ratio ≥21% was related to tumor recurrence with sensitivity of 89% and specificity of 70% (p = 0.006). Patients with LN metastases in the lateral cervical compartment only had significantly lower LNR (14.5%) compared to those with both central and lateral cervical metastases (39.5%) (p = 0.004) and exhibited no tumor recurrence. Increased Ki-67 index was significantly related to LNR ≥21% (p = 0.023) but was not associated with N stage.

CONCLUSIONS

The Ki-67 proliferation index and LNR may better reflect the malignant behavior of PTC compared to the anatomical classification of LN metastases solely.

Machine learning-based prediction model using clinico-pathologic factors for papillary thyroid carcinoma recurrence

This study analyzed the prognostic significance of clinico-pathologic factors, including the number of metastatic lymph nodes (LNs) and lymph node ratio (LNR), in patients with papillary thyroid carcinoma (PTC), and attempted to construct a disease recurrence prediction model using machine learning techniques. We retrospectively analyzed clinico-pathologic data from 1040 patients diagnosed with PTC between 2003 and 2009. We analyzed clinico-pathologic factors related to recurrence through logistic regression analysis. Among the factors that we included, only sex and tumor size were significantly correlated with disease recurrence. Parameters such as age, sex, tumor size, tumor multiplicity, ETE, ENE, pT, pN, ipsilateral central LN metastasis, contralateral central LNs metastasis, number of metastatic LNs, and LNR were input for construction of a machine learning prediction model. The performance of five machine learning models related to recurrence prediction was compared based on accuracy. The Decision Tree model showed the best accuracy at 95%, and the lightGBM and stacking model together showed 93% accuracy. Among those factors mentioned above, LNR and contralateral LN metastasis were used as important features in all machine learning prediction models. We confirmed that all machine learning prediction models showed an accuracy of 90% or more for predicting disease recurrence in PTC. LNR and contralateral LN metastasis were used as important features for constructing a robust machine learning prediction model. In the future, we have a plan to perform large-scale multicenter clinical studies to improve the performance of our prediction models and verify their clinical effectiveness.

Factors Affecting Central Node Metastasis and Metastatic Lymph Node Ratio in Papillary Thyroid Cancer

OBJECTIVE

Despite the growing evidence that metastatic lymph node ratio (MLNR) is a valuable predictor for the prognosis of papillary thyroid carcinoma, it has not yet been fully determined which factors give the ratio predictive value independent of the number of metastatic lymph nodes (MLNs).

STUDY DESIGN

Retrospective cohort study.

SETTING

A comprehensive cancer center.

METHODS

Recurrence and clinicopathologic factors were analyzed in 2409 patients with papillary thyroid carcinoma who underwent total thyroidectomy and central node dissection.

RESULTS

Cutoff values of MLNs ≥2 and MLNR ≥28.2% increased the recurrence risk (hazard ratio [95% CI], 9.97 [4.73-21.0] and 11.4 [5.53-23.3], respectively). Younger age, male sex, multifocality, tumor size, lymphatic and vascular invasion, and gross extrathyroidal extension positively correlated with MLN and MLNR (all P < .05). Meanwhile, lymphocytic thyroiditis negatively correlated with MLNR in female patients (P < .001), by increasing total lymph node yields as compared with papillary thyroid carcinoma without lymphocytic thyroiditis. In multivariate analysis, younger age, tumor size, and lymphatic invasion remained significant in male and female patients for MLN and MLNR; lymphocytic thyroiditis was also significantly correlated with MLNR in female patients.

CONCLUSION

Our study demonstrates that MLN and MLNR are independently observed prognostic markers for tumor recurrence. However, lymphocytic thyroiditis in female patients seems to have lower MLNR by increasing total lymph node yields. In light of their association, a different cutoff for MLNR needs to be applied according to the presence or absence of underlying lymphocytic thyroiditis in the use of MLNR for predicting the recurrence.

LEVEL OF EVIDENCE

4.

Differentiated Thyroid Cancer: The Role of ATA Nodal Risk Factors in N1b Patients

OBJECTIVES/HYPOTHESIS

Nodal involvement is frequent in patients with differentiated thyroid cancers (DTCs), but its prognostic relevance is not univocal. Some characteristics of nodal metastases can increase the risk of recurrence. We attempted to quantify the impact on survival of nodal factors included in the American Thyroid Association (ATA) risk stratification system in N1b patients with DTC.

STUDY DESIGN

Retrospective study.

METHODS

A retrospective analysis of patients affected by DTC who underwent therapeutic lateral neck dissection (ND) was performed. The impact on the prognosis of the number of positive lymph nodes (LNs), dimension of nodal metastasis, and microscopic and macroscopic extranodal extension (miENE and maENE, respectively) was investigated.

RESULTS

The study included 347 N1b patients who underwent 401 therapeutic lateral NDs. Mean number of positive LNs was nine, mean nodal ratio was 0.27, and mean diameter of metastasis was 15.5 mm. ENE was detected in 25.9% of patients (22.5% miENE and 3.5% maENE). In univariate analysis, the presence of maENE had an impact on disease specific survival (DSS) (P = .023); increasing number of positive LNs affected DSS and locoregional control (LRC) (P = .009 and =.006, respectively); increasing metastatic node dimension was a risk factors for overall survival, DSS, and metastases free survival (MFS) (P = .05, =.013 and =.016). In multivariate analysis, number of positive LNs and LN dimension were independent risk factors for LRC and MFS, respectively (HR 1.1, P = .028; HR 1.1, P = .026).

CONCLUSIONS

In our analysis on a cohort of N1b patients, the number of positive LNs and LN dimension were confirmed as independent risk factors for locoregional and distant recurrence, respectively.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E1029-E1034, 2021.

Prophylactic lymph node dissection in clinically N0 differentiated thyroid carcinoma: example of personalized treatment

Considering the 'differentiated thyroid carcinoma (DTC) epidemic', the indolent nature of DTC imposes a treatment paradigm shift toward elimination of recurrence. Lymph node metastases in cervical compartments, encountered in 20-90% of DTC, are the main culprit of recurrent disease, affecting 5-30% of patients. Personalized risk-stratified cervical prophylactic lymph node dissection (PLND) at initial thyroidectomy in DTC with no clinical, sonographic or intraoperative evidence of lymph node metastases (clinically N0) has been advocated, though not unanimously. The present review dissects the controversy over PLND. Weighing the benefit yielded from PLND up against the PLND-related morbidity is so far hampered by the inconsistent profit yielded by PLND and the challenging patient selection. Advances in tailoring PLND are anticipated to empower optimal patient care.

Risk Factors and Outcomes of Postoperative Recurrent Well-Differentiated Thyroid Cancer: A Single Institution's 15-Year Experience

OBJECTIVE

Identify risk factors and outcomes of recurrent well-differentiated thyroid cancer.

STUDY DESIGN

Retrospective case-control analysis.

SETTING

Tertiary care academic center in Nashville, Tennessee.

SUBJECTS AND METHODS

This single-center analysis reviews 478 patients who underwent initial surgical management of well-differentiated thyroid carcinoma between 2002 and 2017. Patients were dichotomized with or without recurrent well-differentiated thyroid cancer. Demographic and clinicopathologic risk factors were carefully reviewed. Univariate, multiple regression, and survival analyses were used to evaluate predictors of recurrence.

RESULTS

Thirty-eight patients (7.9%) who received initial surgical intervention for well-differentiated thyroid carcinoma at our institution recurred, with an average time to recurrence of 24 months. Male sex, tumor size, multifocality, extrathyroidal extension, lymphovascular invasion, number of positive lymph nodes, and low lymph node yield were all significantly associated with locoregional recurrence (P < .05). Multiple regression analysis showed that extrathyroidal extension, number of positive lymph nodes, and low lymph node yield were independent factors predictive of posttreatment recurrence (P < .05). Metastatic lymph node ratio, the ratio of positive lymph nodes extracted to lymph node yield, of ≥0.3 is associated with increased risk of recurrence (P < .001) and decreased 5-year recurrence free survival (P < .001).

CONCLUSION

Extrathyroidal extension, number of positive lymph nodes, and low lymph node yield are independent clinicopathologic risk factors for postoperative recurrence of well-differentiated thyroid cancer. Metastatic lymph node ratio is uncommonly used but can be an important prognosticator of recurrence. Patients with metastatic lymph node ratio ≥0.3 should be counseled on their increased risk of recurrence and should undergo close surveillance following surgery.

Lymph node characteristics of 6279 N1 differentiated thyroid cancer patients

PURPOSE

This study examined the clinicopathological characteristics of 6279 N1 differentiated thyroid cancer (DTC) patients who underwent operations in our center.

METHODS

This was a retrospective longitudinal analysis. We categorized the DTC on the basis of various lymph node (LN) characteristics. Logistic regression models and multiple linear regression models were used for the correlation analysis.

RESULTS

A total of 3693 (58.8%) N1a patients and 2586 (41.1%) N1b patients were included. Patients with N1b disease had larger metastatic foci (0.5 vs. 0.15 cm), a greater number of metastatic LNs (5 vs. 2), a greater number of dissected LNs (25 vs. 7), and a smaller lymph node ratio (NR, number of positive LNs / number of sampled LNs) (23.1% vs. 28.6%) than patients in stage N1a. Comparing the clinicopathological features, we found that male, increased tumor size, multifocality, and thyroiditis increased the risk of stage N1b disease (P<0.05). Sex, multifocality, capsular infiltration, and tumor size were associated with the size of the metastatic LNs (P<0.05). Sex, capsular infiltration, and nodular goiter were associated with the NR (P<0.05). Male sex, tumor located in inferior lobe, maximal tumor diameter (MTD) <1cm, and nodular goiter were independent predictors for skip metastases (P<0.05). MTD <1cm, central neck metastasis and advanced age were independent predictors for bilateral lateral neck metastasis (BLNM) (P<0.05).

CONCLUSION

The LN characteristics of stage N1a and N1b disease were associated with significantly different features, such as sex, tumor size, multifocality, capsular infiltration, and nodular goiter.

The extent of lymph node yield in central neck dissection can be affected by preoperative and intraoperative assessment and alter the prognosis of papillary thyroid carcinoma

Background

Lymph node yield (LNY) was implemented in the stratification of papillary thyroid cancer (PTC) patients. The effect of LNY may be related to the extent of surgery. This study aims to identify influencing factors for LNY in central compartment neck dissection (CND).

Methods

Data of 13 712 consecutive PTC patients were analyzed retrospectively. Risk factors for LNY in CND and distribution characteristics of LNY were evaluated. Its relationship with prognosis was studied in another cohort of 136 cases.

Results

LNY in therapeutic CND was significantly higher than prophylactic CND (Unilateral: 5.55 ± 3.79 vs 3.41 ± 2.77; Bilateral: 8.90 ± 5.10 vs 6.47 ± 4.17, P < .001). Other independent factors included extranodal extension (ETE), tumor size, and concurrent Hashimoto's thyroiditis. The inconsistency distribution of LNY in bilateral CND was associated with preoperative and intraoperative assessment. Patients with significant difference between major and minor LNY suffered from poorer prognosis (10y‐RFS: 58.3% vs 92.0%; HR = 6.719, 95%, P < .0001).

Conclusions

CND surgical procedure, ETE, and Hashimoto's thyroiditis were independent factors of LNY. Inconsistent distribution of LNY was associated with prognosis of bilateral PTC patients. The impact of preoperative and intraoperative assessment on the actual extent of CND can be used to explain the relationship between LNY and PTC prognosis.

Predicting factors for central or lateral lymph node metastasis in conventional papillary thyroid microcarcinoma

BACKGROUND

Optimal management for papillary thyroid microcarcinoma (PTMC) remains controversial. The purpose of this study was to explore risk factors predictive of cervical lymph node metastasis in conventional PTMCs.

METHODS

Conventional PTMC patients (n = 2,404) undergoing surgery between 2010 and 2017 were grouped and analyzed according to the positivity of cervical lymph node.

RESULTS

Central lymph node (CLN) metastases and lateral lymph node (LLN) metastases were observed in 915 (38.1%) and 184 (7.7%) cases, respectively. Multivariate analysis found that male (odds ratio [OR] = 1.974, p < 0.001), younger age (OR = 1.601, p < 0.001), tumor size (OR = 1.935, p < 0.001), extrathyroidal extension (ETE) (OR = 1.647, p < 0.001), multifocality (OR = 1.416, p < 0.001), and intrathyroidal spreading (OR = 3.355, p < 0.001) predicted increased CLN metastasis. In particular, younger age, multifocality, and intrathyroidal spreading were significantly associated with a high number of CLN metastases (n ≥ 5). The presence of CLN metastasis was strongly associated with LLN metastasis (OR = 5.426, p < 0.001).

CONCLUSION

Male, younger age, tumor size, ETE, multifocality, and intrathyroidal spreading predict increased CLN metastasis in PTMCs. In patients with suspicious lateral lymphadenopathy, the presence of CLN metastasis is independently associated with LLN metastasis.

Thyroid Surgery: Whose Domain Is It?

In the United States of America (US), most departments of otorhinolaryngology head and neck surgery have been performing thyroid surgery for many years. In contrast to the US, thyroid surgery is still dominated by general surgeons in most European countries. In numerous university centers, there continues to be friction regarding thyroid surgery. The focus of this editorial is to demonstrate that there is objective data in the literature to suggest that otorhinolaryngologists with appropriate training in head and neck surgery are well suited to perform the entire spectrum of thyroid surgery. The question of who is qualified to perform thyroid surgery is not determined by the basic specialty certification of the surgeon—general or otolaryngology; rather it depends on the training, skill and experience in surgery of the neck, of post-surgical and post-irradiated necks, and of neighboring structures.

Clinical Value of Lymph Node Ratio Integration with the 8th Edition of the UICC TNM Classification and 2015 ATA Risk Stratification Systems for Recurrence Prediction in Papillary Thyroid Cancer

Recently, the 2015 American Thyroid Association (ATA) risk stratification and the 8^th edition of the American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) TNM staging system were released. This study was conducted to assess the clinical value of the lymph node ratio (LNR) as a predictor of recurrence when integrated with these newly released stratification systems, and to compare the predictive accuracy of the modified systems with that of the newly released systems. The optimal LNR threshold value for predicting papillary thyroid cancer (PTC) recurrence was 0.17857 using the Contal and O'Quigley method. The 8^th edition of the AJCC/UICC TNM staging system with the LNR and the 2015 ATA risk stratification system with the LNR were significant predictors of recurrence. Furthermore, calculation of the proportion of variance explained (PVE), the Akaike information criterion (AIC), Harrell's c index, and the incremental area under the curve (iAUC) revealed that the 8^th edition of the TNM staging system with the LNR, and the 2015 ATA risk stratification system with the LNR, showed the best predictive performance. Integration of the LNR with the TNM staging and the ATA risk stratification systems should improve prediction of recurrence in patients with PTC.

Association of Lymph Node Density With Survival of Patients With Papillary Thyroid Cancer

Importance

Lymph node metastases are common in papillary thyroid cancer (PTC), yet the impact of nodal metastases on survival remains unclear. Lymph node density (LND) is the ratio between the number of positive lymph nodes excised and the total number of excised lymph nodes. Lymph node density has been suggested as a prognostic factor in many types of cancer.

Objective

To evaluate the prognostic role of LND in PTC.

Design, Setting, and Participants

This cohort study reviewed medical records of patients with PTC who were treated at the University of Texas MD Anderson Cancer Center between January 1, 2000, and December 31, 2015. Survival and recurrence outcomes were calculated by using the Kaplan-Meier method. Significant variables on univariate analysis were subjected to a Cox proportional hazards regression multivariate model.

Main Outcomes and Measures

Primary study outcome was disease-specific survival (DSS); other measurements included overall survival (OS).

Results

The study cohort included data for 2542 patients (1801 [71%] male; median age, 48 years [range, 18-97 years]) with a median follow-up of 55 months (range, 4-192 months). The 10-year disease-specific survival rate was 98% for patients with LND of 0.19 or less, compared with 90% for those with LND greater than 0.19 (effect size, 8%; 95% CI, 4%-15%). The 10-year overall survival was 87% for patients with LND of 0.19 or less, compared with 79% for patients with LND greater than 0.19 (effect size, 8%; 95% CI, 3%-15%). Multivariable analysis revealed that LND greater than 0.19 was independently associated with an adverse DSS (hazard ratio [HR], 4.11; 95% CI, 2.11-8.97) and OS (HR, 1.96; 95% CI, 1.24-4.11). Subgroup analysis of patients with 18 or more lymph nodes analyzed revealed that LND greater than 0.19 remained a significant marker for DSS (HR, 2.94; 95% CI, 1.36-9.81) and OS (HR, 2.26; 95% CI, 1.12-5.34). Incorporating LND into the current American Joint Committee on Cancer staging system successfully stratified risk groups compared with the traditional TNM staging system.

Conclusions and Relevance

This single-institute study demonstrates the reproducibility of LND as a predictor of outcomes in PTC. Lymph node density can potentially assist in identifying patients with poorer survival who may benefit from more aggressive adjuvant therapy.

PROGNOSTIC VALUE OF LYMPH NODE UPTAKE ON PRETREATMENT F-18 FDG PET/CT IN PATIENTS WITH N1B PAPILLARY THYROID CARCINOMA

Objective: The aim of this study was to investigate the prognostic value of metabolic characteristics of metastatic lymph node (LN) using pretreatment F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for patients with papillary thyroid carcinoma (PTC) and metastatic lateral LN (N1b). Methods: Ninety-six PTC patients (female:male = 72:24; median age, 44.5 years) with pathologic N1b who underwent pretreatment FDG PET/CT, total thyroidectomy, and radioactive iodine ablation were retrospectively reviewed. To predict responses to initial therapy and recurrence, clinicopathologic factors and metabolic parameters were reviewed, such as sex, age, tumor size, extranodal extension, number and ratio of metastatic LNs, serum thyroglobulin, and maximum standardized uptake value (SUVmax). Results: Among the 96 PTC patients, 81 (84.4%) were classified into the acceptable response (58 excellent; 23 indeterminate) and 15 (15.6%) into the incomplete response (8 biochemical incomplete; 7 structural incomplete) by the 2015 American Thyroid Association management guideline for differentiated thyroid carcinoma. The multivariate analysis showed that SUVmax of N1b (P = .018), pre-ablation stimulated thyroglobulin level (P = .006), and the ratio of metastatic LNs (P = .018) were related to incomplete response. The cutoff value of each variable was determined by receiver operating characteristic analysis. Nine (9.4%) patients experienced recurrences (median follow-up: 50 months). The Kaplan-Meier analysis revealed that SUVmax of N1b (cutoff value: 2.3; P = .025) and ratio of metastatic LNs (cutoff value: 0.218; P = .037) were significant prognostic factors for recurrence. Conclusion: High SUVmax of N1b cervical LN on pretreatment FDG PET/CT could predict incomplete responses to initial therapy and recurrence in patients with N1b PTC. Abbreviations: ATA = American Thyroid Association; DTC = well-differentiated thyroid carcinoma; FDG = F-18 fluorodeoxyglucose; IQR = interquartile range; LN = lymph node; N1b = metastatic lateral cervical lymph node; PET/CT = positron emission tomography/computed tomography; PTC = papillary thyroid carcinoma; RAI = radioactive iodine; ROC = receiver operating characteristic; SUVmax = maximum standardized uptake value; Tg = thyroglobulin; USG = ultrasonography.

Predicting recurrence of papillary thyroid cancer using the eighth edition of the AJCC/UICC staging system

BACKGROUND

The AJCC/UICC classification is widely used for predicting survival in papillary thyroid cancer (PTC), but has not been evaluated as a predictor of recurrence. The hypothesis of this study was that the eighth edition of the AJCC system can be used in this novel way.

METHODS

All patients in the study underwent surgery for PTC at a high-volume endocrine surgery centre in France between 1985 and 2015. The seventh and eighth editions of the AJCC/UICC staging system for PTC were employed to predict recurrence and disease-specific survival using the Kaplan-Meier and log rank tests.

RESULTS

Among 4124 patients (79·7 per cent female), median age was 50 (i.q.r. 38-60) years; 3906 patients (94·7 per cent) underwent total thyroidectomy, with lymph node dissection in 2495 (60·5 per cent). The eighth edition of the AJCC/UICC staging system placed 91·8, 7·1, 0·4 and 0·7 per cent of patients in stages I-IV respectively. After reclassifying patients from the seventh to the eighth AJCC/UICC edition, the disease was downstaged in 23·8 per cent. Over a median follow-up of 7 years, 260 patients (6·4 per cent) developed recurrent disease, including 5·2 per cent of patients with stage I, 19·6 per cent with stage II, 59 per cent with stage III and 50 per cent with stage IV disease, according to the eighth edition. The eighth edition was a better predictor of recurrence than the seventh edition.

CONCLUSION

The eighth edition of the AJCC/UICC staging system appears to be a novel tool for predicting PTC recurrence, which is a meaningful outcome for this indolent disease. The eighth edition can be used to risk-stratify patients, keeping in mind that other molecular and pathological predictive factors must be integrated into the assessment of recurrence risk.

Lymph node ratio predicts recurrence in pediatric papillary thyroid cancer

BACKGROUND

Regional lymph node (LN) metastasis at the time of presentation plays a significant role in predicting recurrence in patients with papillary thyroid cancer (PTC). Multiple studies in the adult population have demonstrated that the lymph node ratio (LNR) in both the central and lateral neck can improve the accuracy of recurrence prediction, but this ratio has not been studied in the pediatric population. In this study, we sought to investigate the LNR in the central and lateral compartments as a prognostic predictor for recurrence in pediatric patients with PTC.

METHODS

A retrospective analysis of pediatric patients (≤21 years old) at a single institution between 2002 and 2014 who underwent total thyroidectomy with prophylactic central neck dissection (TTpCND) with at least 3 sampled nodes or total thyroidectomy with unilateral modified radical neck dissection (TTMRND) with at least 10 sampled nodes, and on whom at least 24 months of follow up data were available was performed. The LNR was defined as the ratio of metastatic LNs to total number of investigated LNs. Recurrence after TTpCND and TTMRND was examined separately as a function of LNR, using the value of 0.45 as a cutoff.

RESULTS

Forty-eight patients met inclusion criteria. Thirty-two underwent TTpCND, and sixteen underwent TTMRND. Median age at time of operation was 17 years (range 6-20), and median duration of follow-up was 53.5 months (range 24-183). In the TTpCND, LNR ranged from 0 to 1.0. There were two recurrences among the eight patients (25%) undergoing TTpCND in patients with LNRs >0.45 and a single recurrence among the 24 patients (4.2%) undergoing TTpCND with an LNR ≤0.45. In the TTMRND, LNR ranged from 0.1 to 1.0. There were 3 recurrences in 12 patients with LNR ≤0.45 (30.8%%) and 4 recurrences in 4 patients with LNR >0.45 (100%) (p = 0.03).

CONCLUSIONS

Although limited by small sample size, LNR may be a useful predictor to stratify the likelihood of recurrence in pediatric patients undergoing TTpCND or TTMRND for pathologic N1a or N1b PTC.

TYPE OF STUDY

Prognosis study / retrospective case series.

LEVEL OF EVIDENCE

Level IV.

Identifying risk factors of lateral lymph node recurrence in clinically node-negative papillary thyroid cancer

There is still debate regarding the role of routine central lymph node (LN) dissection in treating clinically node-negative papillary thyroid cancer (PTC). The aim of this study was to investigate the risk factors for lateral recurrence after total thyroidectomy and prophylactic bilateral central LN dissection in clinically node-negative PTC patients.We retrospectively collected the medical records of 1406 PTC patients who underwent total thyroidectomy and prophylactic bilateral central LN dissection between January 2004 and December 2008. We used Cox- proportional hazards regression analyses to inspect the predictive factors for recurrence.During a median follow-up of 107 months (range, 13-164 months), 68 (4.8%) and 37 (2.6%) patients experienced recurrence in any lesion and in lateral neck LN, respectively. Male, main tumor size >1 cm, nodal factors (pathologic N1a, positive delphian LN, and LN ratio >0.15), lymphovascular invasion, and extrathyroidal extension (ETE) were significantly associated with lateral neck LN recurrence in univariate analysis. Multivariate analysis showed that male (hazard ratio [HR], 2.217; 95% confidence interval [CI], 1.057-4.647; P = .035), main tumor size >1 cm (HR, 2.257; 95% CI, 1.138-4.476; P = .020), pathologic N1a (HR, 5.957; 95% CI, 2.573-13.789; P < .002), minor ETE (vs no ETE; HR, 3.027; 95% CI, 1.315-6.966; P = .009), and gross ETE (vs no ETE; HR, 4.058; 95% CI, 1.685-9.774; P = .002) were independent predictors for lateral neck LN recurrence.Among patients with pathologic N1a, those with LN ratio of more than 0.55 had worse lateral neck LN recurrence-free survival. Lateral neck LN recurrence in clinically node-negative PTC patients is predicted by the factors of male, main tumor size >1 cm, ETE, and pathologic N1a.

Identifying risk factors for recurrence of papillary thyroid cancer in patients who underwent modified radical neck dissection

Background

Papillary thyroid cancer (PTC) patients with ipsilateral neck metastatic lymph node (LN) and those with contralateral neck metastatic LN belong to N1b. Only a few studies have reported on comparisons with regard to laterality of metastatic lateral LN. The aim of this study was to evaluate predictive factors for contralateral neck LN metastasis and to determine prognostic factors for recurrence in PTC patients with N1b.

Methods

This retrospective study reviewed the medical records of 390 PTC patients who underwent total thyroidectomy and central LN dissection plus ipsilateral or bilateral modified radical neck dissection (MRND) between January 2004 and December 2012.

Results

During a median follow-up of 81 (range, 6–156) months, 84 patients had a recurrence in any lesion. Male gender, a main tumor of more than 2 cm, number of metastatic central LN, number of harvested and metastatic lateral LN, total LN ratio, multifocality, bilaterality, and gross ETE had significance in the patients who underwent bilateral MRND. In multivariate analysis according to recurrence, patients with LN ratio > 0.44 in the central compartment (hazard ratio [HR], 1.890; 95% confidence interval [CI], 1.124–3.178; p = 0.015), LN ratio > 0.29 in the lateral compartment (HR, 2.351; 95% CI, 1.477–3.743; p < 0.001), and multifocality (HR, 1.583; 95% CI, 1.030–2.431; p = 0.036) were associated with worse RFS. However, the type of MRND was statistically significant only in univariate analysis.

Conclusions

Recurrence in N1b PTC patients is predicted by central neck LN ratio > 0.44, lateral neck LN ratio > 0.29, and multifocality of tumors. We suggest that patients with these factors should receive short-term follow-up using image modalities like ultrasonography and computed tomography.

Low-Dose Radioactive Iodine Ablation Is Sufficient in Patients With Small Papillary Thyroid Cancer Having Minor Extrathyroidal Extension and Central Lymph Node Metastasis (T3 N1a)

PURPOSE

The aim of this study was to evaluate the effectiveness of low-dose radioactive iodine (RAI) ablation in patients with small papillary thyroid cancer (PTC) exhibiting microscopic extrathyroidal extension (mETE) and central lymph node (CLN) metastasis.

METHODS

Among patients who underwent RAI ablation between March 2007 and February 2014, those who had small PTCs (≤2 cm), as well as mETE and CLN metastasis (T3 N1a M0), were enrolled. Response to ablation and long-term outcomes were assessed and compared according to the administered RAI dose. Factors associated with unsuccessful ablation were also determined.

RESULTS

A total of 180 patients were included in the study. Eighty-eight patients had been treated with 1110 MBq (low-dose group) and 92 with 2960 MBq (high-dose group) of RAI. There were no significant differences in the responses to ablation (P = 0.810) and long-term outcomes (P = 0.663) between both groups. Among all patients enrolled, 13 did not achieve successful ablation at long-term follow-up. Logistic regression found that a high ratio of metastatic nodes was a significant factor for predicting unsuccessful ablation.

CONCLUSIONS

Low-dose RAI ablation did not produce significantly different responses or long-term outcomes in patients with small PTCs exhibiting mETE and CLN metastasis. These findings suggest that low-dose ablation may be sufficient in this specific group of intermediate-risk patients, although careful selection is required for patients with a high ratio of metastatic nodes.

Optimizing treatment for children and adolescents with papillary thyroid carcinoma in post-Chernobyl exposed region: The roles of lymph node dissections in the central and lateral neck compartments

There is lack of data to predict lymph node metastases in pediatric thyroid cancer. The aims are to study (1) the factors affecting the lymph node metastases in children and adolescence with papillary thyroid carcinoma in region exposed to radiation and (2) to evaluate the predictive significance of these factors for lateral compartment lymphadenectomy. Five hundred and nine patients with papillary thyroid carcinoma underwent total thyroidectomy and lymph nodes resection (central and lateral compartments of the neck) surgery during the period of 1991-2010 in Belarus were recruited. The factors related to lymph node metastases were studied in these patients. In the patients with papillary thyroid carcinoma, increase number of cancer-positive lymph nodes in the central neck compartment were associated with a risk to develop lateral nodal disease as well as bilateral nodal disease. Futhermore, positive lateral compartment nodal metastases are associated with age and gender of the patients, tumour size, minimal extra-thyroidal extension, solid architectonic, extensive desmoplasia in carcinoma, presence of psammoma bodies, extensive involvement of the thyroid and metastatic ratio index revealed after examination of the central cervical chain lymph nodes. The presence of nodal disease, degree of lymph node involvement and the distribution of lymph node metastases significantly increase the recurrence rates of patients with papillary thyroid carcinoma. To conclude, the lymph nodes metastases in young patients with papillary thyroid carcinoma in post-Chernobyl exposed region are common and the pattern could be predicted by many clinical and pathological factors.

Nodal Factors Predictive of Recurrence After Thyroidectomy and Neck Dissection for Papillary Thyroid Carcinoma

BACKGROUND

Lymph node (LN) yield and ratio are considered important predictors of post-treatment outcomes for several human cancers. This study examined the association between nodal factors, including the LN yield and ratio, with recurrence after thyroidectomy plus central compartment neck dissection (ND) for papillary thyroid carcinoma (PTC).

MATERIALS AND METHODS

This retrospective study involved 2384 consecutive patients who underwent a thyroidectomy plus central compartment ND combined with (n = 440) or without lateral compartment ND at the authors' tertiary referral center between 2006 and 2012. The number of harvested LNs, as well as other tumor and nodal findings, were carefully reviewed. Univariable and multivariable Cox proportional hazards regression models were conducted to predict recurrence and its association with clinicopathologic variables.

RESULTS

All nodal factors, including the positive number of LNs, ratio, and extranodal extension, were significantly associated with nodal and any-site recurrence after thyroidectomy, as well as the tumor size and multifocality (p < 0.01). The multivariable analysis showed that tumor size, multifocality, LN ratio, and extranodal extension were independent factors predictive of post-treatment recurrence (p < 0.05). The LN yield was higher in patients with nodal recurrence but did not significantly affect the nodal recurrence. Patients with a LN ratio >0.3 exhibited a 1.7-fold higher risk of post-treatment nodal recurrence than their counterparts (p < 0.01).

CONCLUSIONS

LN ratio is an independent determinant predictive of nodal and any-site recurrence following thyroidectomy for PTC.

Prognostic value of lymph node ratio in metastatic papillary thyroid carcinoma

Objective:

Cervical metastases in papillary thyroid carcinoma are associated with increased recurrence. However, their effect on survival remains controversial. This study evaluated literature on the prognostic value of lymph node ratio for loco-regional recurrence and survival in metastatic papillary thyroid carcinoma.

Methods:

The PubMed database was systematically searched using the terms ‘papillary thyroid carcinoma’ and ‘lymph node ratio’. Articles addressing the association between lymph node ratio and loco-regional recurrence or survival were identified.

Results:

Nine retrospective studies were included, comprising 12 400 post-thyroidectomy and neck dissection papillary thyroid carcinoma patients (median age, 48.6 years; 76 per cent females). Lymph node ratio was associated with worse recurrence-free survival in 60 and 75 per cent of studies investigating the effect of central compartment metastases and both central and lateral compartment metastases on recurrence-free survival, respectively. One large population-based study showed an association between lymph node ratio and disease-specific mortality in N1nodal disease, but failed to maintain the same association when N1bpatients were excluded.

Conclusion:

Regional lymph node ratio is an independent predictor for loco-regional recurrence in pathologically staged N1patients with papillary thyroid carcinoma. Patients with a high lymph node ratio should be closely followed up.

Number of Metastatic Lymph Nodes and Ratio of Metastatic Lymph Nodes to Total Number of Retrieved Lymph Nodes Are Risk Factors for Recurrence in Patients With Clinically Node Negative Papillary Thyroid Carcinoma

OBJECTIVES

The number of metastatic lymph nodes (LNs) and the ratio between the number of metastatic LNs and the total number of retrieved LNs (the LN ratio [LNR]) have been proposed as risk factors for recurrence of papillary thyroid carcinoma (PTC). However, the significance of the number of LNs and the LNR in patients with clinically node negative PTC has not been clearly determined. The purpose of this study is to evaluate their significance.

METHODS

We retrospectively analyzed 382 patients with PTC who had undergone total thyroidectomy with prophylactic central neck dissection (CND) between January 2000 and December 2010. We excluded patients with lobectomy, concurrent lateral compartment neck dissection, a follow-up period less than at least 2 years, number of harvested central LNs less than or equal to one, clinically positive LN, distant metastasis, recurrent cancer or other types of malignancy. The correlations between recurrence and various clinicopathologic characteristics including tumor size, extrathyroidal extension (ETE), stage, number of metastatic central LNs, and the LNR were investigated.

RESULTS

After a mean follow-up period of 82.2±26.4 months, recurrence occurred in 14 patients (3.7%). Tumor size ≥20 mm, maximal ETE, presence of central LN metastasis, number of metastatic LNs ≥2, and LNR ≥0.31 correlated with recurrence in the univariate analysis. However, tumor size ≥20 mm, maximal ETE, number of metastatic LNs ≥2, and LNR ≥0.31 were significantly associated with recurrence in the multivariate analysis (hazard ratio=6.61, 7.17, 3.43, and 11.23, respectively).

CONCLUSION

The LNR and the number of metastatic LNs are independent prognostic risk factors for recurrence in patients with clinically node negative PTC, and these factors can be used to guide postoperative adjuvant therapy and follow-up strategy after prophylactic CND.