Mandatory Nodal Evaluation During Resection of Clinical T1a Non-Small Cell Lung Cancers

Background: Recommendations for intraoperative lymph node evaluation are uniform regardless of whether a primary tumor is clinical T1a or T2a according to TNM 8th edition for stage I non-small cell lung cancer (NSCLC). We quantified nodal disease risk in patients with T1a disease (≤1 cm).

Methods: The National Cancer Database was queried for clinical T1a N0 M0 primary NSCLCs ≤1 cm undergoing lobectomy with mediastinal nodal evaluation from 2004-2014. Nodal disease risk was analyzed as a function of demographics and tumor characteristics.

Results: Among 2157 cases, 6.7% had occult nodal disease: 5.1% occult N1 and 1.6% N2. Adenocarcinoma (7.5%), large cell carcinoma (25%), and poor differentiation (11.8%) or undifferentiated/anaplastic (25.0%) had high rates of combined pN1 and N2 disease (P < .001). In univariable analysis, odds of pathologic N1, N2, or N1/N2 nodal disease with respect to N0 was greatest for large cell carcinoma (ref. adenocarcinoma odds ratio [OR] 4.31, 3.62, 4.12 respectively; all P < .05), and anaplastic grade (OR 10.71, 13.09, 11.55). Bronchoalveolar adenocarcinomas had the lowest odds (OR 0.41, 0.11, 0.32) and squamous cell carcinoma had lower odds for N2 (OR 0.29, all P < .05). In multivariable analysis only bronchoalveolar adenocarcinomas had lower odds of pathologic N2 and N1/N2 disease with respect to N0. Worsening grade remained significant for pathologic N1 and N1/N2 disease (both P < .05).

Conclusions: A significant rate (6.7%) of occult nodal disease is present in primary NSCLCs ≤1 cm. Risk increases with certain histology and worsening grade. We recommend mandatory systematic hilar and mediastinal nodal evaluation for T1a NSCLC tumors for accurate staging and adjuvant therapy.