Development and internal validation of a clinical nomogram incorporating quantitative CT features for predicting malignancy in pulmonary nodules ≤ 3 cm.

BACKGROUND

Accurate differentiation between benign and malignant pulmonary nodules ≤ 3 cm remains a clinical challenge. This study aimed to develop and internally validate a clinically interpretable nomogram integrating clinical variables and quantitative computed tomography (CT) features for predicting malignancy in pulmonary nodules.

METHODS

This retrospective single-center study included 1,419 patients with pulmonary nodules ≤ 3 cm who underwent surgical resection between January 2012 and July 2025 with pathologic confirmation. The cohort was randomly divided into a training set (n = 994) for model development and a validation set (n = 425) for internal validation. Clinical data, conventional imaging findings, serum biomarkers, and quantitative CT measurements from preoperative thin-section CT were collected. Multivariable logistic regression was used to identify variables associated with malignancy and construct the nomogram.

RESULTS

Among the 1,419 nodules, 1,150 (81.0%) were malignant and 269 (19.0%) were benign. The final nomogram incorporated seven variables: suspicious radiologic features, nodule size, sex, symptoms at detection, consolidation-to-tumor ratio, minimum CT attenuation, and age. Age was retained in the final model on clinical grounds despite lacking statistical significance in multivariable analysis. Suspicious radiologic features (adjusted odds ratio [aOR] = 6.61, 95% confidence interval [CI]: 4.51-9.84; P < 0.001), nodule diameter > 2 cm (aOR = 4.07, 95% CI: 2.16-7.62; P < 0.001), female sex (aOR = 1.69, 95% CI: 1.23-2.33; P = 0.001), asymptomatic presentation (aOR = 0.48, 95% CI: 0.34-0.69; P < 0.001), consolidation-to-tumor ratio > 0.50 (aOR = 0.20, 95% CI: 0.06-0.61; P = 0.005), and minimum CT attenuation per 100-HU increase (aOR = 0.82, 95% CI: 0.74-0.92; P < 0.001) were independently associated with malignancy. The nomogram showed good discrimination, with area under the receiver operating characteristic curve values of 0.809 in the training set and 0.782 in the validation set. Calibration analysis showed agreement between predicted and observed risks, and decision curve analysis supported usefulness.

CONCLUSIONS

We developed and internally validated a clinical nomogram incorporating quantitative CT features for malignancy risk estimation in surgically resected pulmonary nodules ≤ 3 cm. The model showed good discrimination, calibration, and potential utility in a malignancy-enriched preoperative cohort. External validation in broader, less selected, screening-detected, incidental, and multicenter populations is warranted before routine clinical application.