Abstract / Summary
Abstract Background Distant metastasis is the leading cause of death after curative resection for colorectal cancer (CRC). Accurately distinguishing primary lung cancer (PLC) from solitary lung metastasis (SLM) in patients with solitary pulmonary nodules (SPNs) remains clinically challenging due to the limitations of biopsy and conventional imaging. This study aimed to explore the diagnostic value of basic ¹⁸F‑fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F‑FDG PET/CT) parameter-based model for differentiating these two entities, so as to provide evidence for clinical differential diagnosis. Results This cohort included 101 patients (75 males, 26 females), with a mean age of 62.31 ± 9.52 years (range: 32–80 years). Pathological verification revealed 53 SLMs and 48 PLCs. The receiver operating characteristic (ROC)-derived area under the curve (AUC) of the PET/CT parametric model, clinical model, and combined model was 0.757 (95% Confidence Interval [CI]: 0.663–0.851), 0.768 (95% CI: 0.676–0.861), and 0.871 (95% CI: 0.800–0.942), respectively. After 1000 bootstrap internal validation, the corrected AUCs were 0.757 (95% CI: 0.666–0.851), 0.767 (95% CI: 0.687–0.867), and 0.870 (95% CI: 0.809–0.949), respectively. The combined model exhibited significantly superior diagnostic performance compared with the PET/CT parametric model (0.871 vs. 0.757, P = 0.006) and the clinical model alone (0.871 vs. 0.768, P = 0.003). No statistically significant difference was observed between the PET/CT parametric model and the clinical model (0.757 vs. 0.768, P = 0.860). Conclusions Basic ¹⁸F‑FDG PET/CT parametric model enables effective discrimination between PLC and SLM presenting as SPNs in post-operative CRC patients. The combined model integrating PET/CT parameters and independent clinical risk factors markedly improves diagnostic efficacy relative to single models, showing favourable clinical practicability.