The Impact of Pathologically Positive Lymph Nodes in the Clinically Negative Neck: An Analysis of 39,301 Patients with Papillary Thyroid Cancer

Abstract

Purpose

Management of patients with low-risk papillary thyroid cancer (PTC) with clinically uninvolved lymph nodes (cN0 LNs), but who harbor metastatic central LNs (pN1a), remains unclear. The number of central LNs examined, radioactive iodine (RAI) utilization, and survival were compared across cN0 patients based on pN stage: pN0 (negative) versus pNx (unknown) versus pN1a (pathologically positive).

Methods

Adults with a PTC ≥1 cm who were cN0 preoperatively were compared based on surgical pathology using the National Cancer Data Base (NCDB; 2003–2011), after univariate and multivariate adjustment. Overall survival (OS) was examined using Kaplan–Meier curves, the log-rank test, and Cox proportional hazards modeling.

Results

Overall, 39,301 patients were included; median tumor size was 1.9 cm. More LNs were examined for pN1a versus pN0 diagnosis (pN1a median = 5 LNs vs. pN0 median = 2 LNs; p < 0.0001), with a median of two central LNs found to be positive on surgical resection. Compared with pN0, pN1a patients were 78% more likely to receive RAI (odds ratio 1.78, 95% confidence interval [CI] 1.65–1.91; p < 0.0001). After adjusting for receipt of RAI, no difference in OS was observed for pN1a versus pN0 or pNx patients (p = 0.72). Treatment with RAI was associated with improved OS (hazard ratio 0.78, 95% CI 0.62–0.98, p = 0.03), but the effect of RAI did not differ based on pN stage (interaction p = 0.67).

Conclusion

More LNs were examined for positive versus negative pN diagnosis in patients with cN0 PTC. Unsuspected central neck nodal metastases in cN0 PTC patients are associated with increased RAI utilization, but no survival difference.

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