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Original Investigation
November 30, 2017

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

Author Affiliations
  • 1Division of Surgery, Department of Head and Neck Surgery, University of Texas MD Anderson Cancer Center, Houston
  • 2Division of Internal Medicine, Department of Endocrine Neoplasia and Hormonal Disorders, University of Texas MD Anderson Cancer Center, Houston
  • 3Division of Surgery, Department of Endocrine Surgical Oncology, University of Texas MD Anderson Cancer Center, Houston
JAMA Otolaryngol Head Neck Surg. 2018;144(2):108-114. doi:10.1001/jamaoto.2017.2416
Key Points

Question  Is there an association between lymph node density (LND)—the ratio of the number of positive lymph nodes to the total number of nodes excised—and survival in patients with papillary thyroid cancer?

Findings  In a cohort of 2542 patients, central neck LND reliably stratified patients according to risk of death. Incorporating LND into the current American Joint Committee on Cancer staging system successfully stratified risk groups compared with the traditional TNM staging system.

Meaning  Lymph node density can be used as a complementary prognostic tool to assess risk of disease-related death in patients with papillary thyroid cancer.

Abstract

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%] female; 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.

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