Adequacy of Lymph Node Yield for Papillary Thyroid Cancer: An Analysis of 23,131 Patients

Threshold numbers for defining adequacy of lymph node (LN) yield have been determined for evaluation of occult nodal disease during papillary thyroid cancer (PTC) surgery. This study assesses the prevalence of adequate LN yield and estimates its association with patient clinicopathologic characteristics.

Adult patients with cN1 pT1b or pT2 and cN0 or cN1 pT3 M0 PTC ≥1 cm who received surgery with ≥1 LN resected were identified from the National Cancer Database, 2004-2015. Adequate yield was defined as removing ≥6, 9, and 18 LNs for pT1b, pT2, and pT3 stages, respectively, based on recently published literature. Univariable and multivariable logistic regression were used to determine factors associated with adequate yield.

A total of 23,131 patients were included; 7544 (32.6%) had adequate LN yield. Rate of adequate yield increased from 19.9% to 36.6% over time. After adjustment, patients at academic facilities were more likely to have adequate yield than those at community centers [OR 1.94 (95% CI 1.55-2.41), P < 0.001]. Patients with more advanced tumors were less likely to have adequate yield (pT1b: 75.9% versus pT2: 64.5% versus pT3: 24.6% adequate LN yield, P < 0.001). Patients with adequate LN yield were 0.89 times likely to receive radioactive iodine compared with those with inadequate yield [OR 0.98 (95% CI 0.81-0.98), P = 0.02].

The rate of adequate LN yield has increased over time, but only a minority of lymphadenectomies performed for PTC can be defined as adequate. Disparities still exist based on patient and facility characteristics; patients with more advanced tumors appear less likely to have adequate LN yield.