**Background:** Lung cancer has high morbidity and mortality worldwide. While chest CT screening improves detection, it has high false-positive rates, leading to unnecessary procedures and patient anxiety. Metabolic reprogramming is a hallmark of cancer, and amino acid and carnitine profiles may serve as objective biomarkers. This study aimed to develop a nomogram using metabolic profiling to discriminate early-stage lung cancer from benign lung nodules.
**Methods:** This retrospective cohort study recruited 848 participants (478 lung cancer, 370 benign nodules) screened by chest CT between April 2018 and December 2020 at the Second Affiliated Hospital of Dalian Medical University. Participants were randomly divided into training (n=594; 334 lung cancer, 260 benign) and validation (n=254; 144 lung cancer, 110 benign) sets at a 7:3 ratio. Blood samples were collected after overnight fasting. LC-MS/MS measured 20 amino acids and 27 carnitines. Variables with statistically significant differences between groups were selected for LASSO regression to avoid overfitting. Stepwise logistic regression identified 13 independent predictors for the nomogram. Model performance was evaluated using ROC curves, calibration curves with 1000 bootstrap resamples, and decision curve analysis.
**Key Results:** Thirty variables showed statistically significant differences between lung cancer and benign nodule groups. LASSO regression reduced these to 25 variables. Multivariate logistic regression identified 13 independent predictors: age (OR 1.065, 95%CI 1.043–1.087, P<0.001), sex (OR 2.274, 95%CI 1.405–3.680, P=0.001), ornithine (OR 0.952, 95%CI 0.926–0.980, P=0.001), tyrosine (OR 1.025, 95%CI 1.007–1.044, P=0.008), glutamine (OR 1.010, 95%CI 1.003–1.017, P=0.003), valine (OR 1.015, 95%CI 1.006–1.024, P=0.001), serine (OR 0.948, 95%CI 0.930–0.967, P<0.001), asparagine (OR 0.977, 95%CI 0.962–0.992, P=0.003), arginine (OR 1.098, 95%CI 1.037–1.162, P=0.001), methylmalonylcarnitine (C4DC) (OR 0.055, 95%CI 0.014–0.218, P<0.001), tetradecenoylcarnitine (C14:1) (OR 2.890, 95%CI 1.621–5.153, P<0.001), 3-hydroxyisovaleryl carnitine/2-methyl-3-hydroxybutyrylcarnitine (C5OH) (OR 1.386, 95%CI 1.023–1.877, P=0.035), and hydroxybutyrylcarnitine (C4OH) (OR 0.384, 95%CI 0.189–0.779, P=0.008). The nomogram achieved an AUC of 0.836 (95%CI 0.830–0.890) in the training set and 0.860 after 1000 bootstrap resamples. In the validation set, AUC was 0.781 (95%CI 0.722–0.841) and remained 0.781 after bootstrap resampling. Individual AUCs ranged from 0.552 (arginine) to 0.731 (ornithine). Calibration curves showed good agreement between predicted and actual values. Decision curve analysis demonstrated net benefit superior to baseline within the threshold probability range of 15% to 93%.
**Clinical Implications:** This nomogram provides a non-invasive, objective tool using peripheral blood metabolites to discriminate early-stage lung cancer from benign lung nodules. It avoids subjective imaging interpretation and may reduce unnecessary invasive procedures. The model includes four acylcarnitines (C4DC, C4OH, C5OH, C14:1) incorporated into a lung cancer prediction model for the first time. Limitations include lack of external validation, exclusion of nodule imaging features and smoking history, and suboptimal sensitivity/specificity. Further large-scale multicenter studies are needed before clinical implementation.