Preoperative T-staging flowchart using oral contrast-enhanced transabdominal ultrasound for gastric cancer: single-center prospective study

To standardize oral contrast-enhanced transabdominal ultrasound (OCTU) for preoperative gastric cancer (GC) T staging, this study aimed to identify objective ultrasound indicators to improve diagnostic accuracy and consistency. From December 2023 to December 2024, 150 GC patients undergoing OCTU followed by surgery were prospectively enrolled and divided into training ( n = 116) and testing ( n = 34) set. Two blinded ultrasonographers independently assessed images, evaluating the five-layer gastric wall structure (L1–L5), measuring layer thicknesses, and recording L3 interruption and L5 protrusion. A diagnostic flowchart for T staging was developed and validated, with accuracy compared to contrast-enhanced CT (CECT). OCTU visualized lesions in 144/150 patients (104 males, 46 females; mean age 60.5 ± 9.7 years), with failures in 5 T1a and 1 T1b tumors. L3 thickening difference distinguished T1a, T1b and T2, with cutoffs of 0.11 cm (AUC = 0.957) and 0.23 cm (AUC = 0.910) respectively. L4 thickness difference (cutoff: 0.24 cm, AUC = 0.860) further differentiated T2 from T3. L3 interruption narrows the diagnostic range to T2 and T3. L5 protrusion (cutoff: 0.50 cm, AUC = 0.980) distinguished T3 from T4. The flowchart achieved 78.4% overall accuracy (76.5% in validation), outperforming CECT (66.4%, p = 0.003), with superior performance in early GC (T1a/T1b: 65.2% vs. 39.1%, p = 0.031; 72.0% vs. 48.0%, p = 0.031) and comparable accuracy for advanced GC. An OCTU-based diagnostic flowchart provides validated, accurate T-staging for GC, demonstrating accuracy comparable to or superior to CECT, supporting OCTU’s application for GC assessment. The study has been registered on the Chinese Clinical Trial Registry. The registration number is ChiCTR2300078421. Registration Date: 2023-12-07.