# Preoperative Contrast-enhanced CT Features Associated with Occult Lymph Node Metastasis in Early-Stage Solid Non–Small Cell Lung Cancer

## TL;DR

This study creates a CT-based model to predict hidden lymph node metastasis in early-stage lung cancer, helping tailor surgical strategies.

## Contribution

A novel CT-based nomogram is developed to predict occult lymph node metastasis in early-stage solid NSCLC.

## Key findings

- 22.2% of patients had occult lymph node metastasis, with 47.9% in N1 and 52.1% in N2.
- Key predictors include decreased inner margin ratio, lollipop sign, and tumor-pleura relationship types II and III.
- The nomogram achieved an AUC of 0.81 with 78.1% sensitivity and 73.4% specificity.

## Abstract

To develop and validate a contrast-enhanced CT-based prediction model for
identifying occult lymph node metastasis (OLNM) in patients with
early-stage non–small cell lung cancer (NSCLC), with the goal of
supporting individualized lymph node dissection (LND) strategies.

This retrospective study included patients with preoperative clinical
stage I–IIA (cT1–T2bN0M0) solid NSCLC who underwent
lobectomy with systematic LND between January 2021 and April 2024.
Univariable and multivariable logistic regression analyses were used to
identify independent preoperative CT predictors of OLNM and to construct
a nomogram. Model performance was assessed using the area under the
receiver operating characteristic curve, and specificity was evaluated
at a fixed sensitivity of 95%.

Among 329 patients with solid NSCLC (median age, 65 years; IQR,
58–70 years; 168 male patients), 22.2% (73 of 329) had OLNM,
including 47.9% (35 of 73) with N1 and 52.1% (38 of 73) with N2
metastases. Independent predictors of OLNM were a decreased inner margin
ratio (odds ratio [OR], 0.02; 95% CI: 0.00, 0.10; P
< .001), presence of the lollipop sign (OR, 3.48; 95% CI: 1.87,
6.49; P < .001), and tumor-pleura relationship
type II (OR, 6.95; 95% CI: 2.62, 18.44; P <
.001) and type III (OR, 13.27; 95% CI: 5.11, 34.45; P
< .001). The nomogram achieved an area under the receiver
operating characteristic curve of 0.81 (95% CI: 0.76, 0.87), with a
sensitivity of 78.1% and specificity of 73.4%; specificity was 39.1% at
95% sensitivity.

A contrast-enhanced CT-based nomogram incorporating inner margin ratio,
lollipop sign, and tumor-pleura relationship enabled effective
preoperative risk stratification for OLNM in early-stage solid NSCLC and
may aid in tailoring LND strategies.

Keywords: Imaging Modality, Lung, Neoplasms-Primary,
Thorax

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© The Author(s) 2026. Published by the Radiological Society of
North America under a CC BY 4.0 license.