Solid part size is an important predictor of nodal metastasis in lung cancer with a subsolid tumor

Candidates for preoperative or intraoperative nodal assessment among patients with non-small cell lung cancer (NSCLC) manifesting as a subsolid tumor are not established. The present study was conducted to demonstrate the distribution of nodal metastasis rate according to newly proposed T categories for subsolid tumors, and we further aimed to identify radiologic parameters that can be predictive of nodal metastasis.

We retrospectively reviewed cases of NSCLC manifesting as a subsolid tumor in computed tomography scans in a university-affiliated tertiary hospital between April 2013 and August 2016. All patients underwent mediastinal lymph node dissection during resection surgery. Multivariate analysis was performed among clinical and radiologic parameters.

Of the 269 eligible patients, T-categories were classified as cTis (n = 23, 8.6%), cT1 (n = 203, 75.5%), and cT2 (n = 43, 16.0%). Ten patients (3.7%) had nodal metastasis: pN1 (n = 5, 1.9%), pN2 (n = 5, 1.9%). Nodal metastasis was not observed in tumors with a solid part ≤1.0 cm (cT1mi and cT1a) or in nonsolid tumors ≤3.0 cm (cTis). The nodal metastasis rate in cT1b, cT1c, and cT2 tumors was 6.1% (4/65), 8.3% (1/12), and 11.7% (5/43), respectively. Multivariate analysis showed that a solid part size > 1.5 cm [odds ratio, 5.89; 95% confidence interval, 1.25-27.68, p = 0.025] was significantly associated with nodal metastasis.

We observed nodal metastasis from cT1b tumors (solid part size > 1 cm) among proposed T categories for subsolid tumors and a solid part size is an important radiologic parameter predictive of nodal metastasis in NSCLC manifesting as a subsolid tumor. Considering the low rate of nodal metastasis, pathologic nodal assessment may be unnecessary in early T category tumors with a small solid part size.