Construction of a nomogram for preoperative prediction of occult peritoneal metastasis in advanced gastric cancer based on circulating tumor cells and fibrinogen to albumin ratio

BACKGROUND: Occult peritoneal metastasis (OPM) represents a type of distant metastasis that is often overlooked during the preoperative diagnosis of advanced gastric cancer (AGC). METHODS: We employed the negative enrichment combined with immunofluorescence in situ hybridization (imFISH) technique to detect the number of circulating tumor cells (CTC) in the peripheral blood of patients with AGC. 523 AGC patients were randomly divided into a training set (N = 367) and a validation set (N = 156) in a 7:3 ratio. We constructed a nomogram for predicting OPM risk through multivariate logistic regression. Finally, we evaluated the performance of the nomogram using multi-index cross-validation and clinical decision curve analysis (DCA). RESULTS: The number of CTC and the level of the fibrinogen-to-albumin ratio (FAR) in patients with OPM positivity were significantly higher than those in OPM-negative patients. Multivariate logistic regression analysis revealed that CTC > 4/5 mL, FAR > 0.094, CA125 > 35.000 U/mL, and tumor invasion of the serosal layer were identified as independent risk factors for OPM in AGC. The areas under the ROC curve of the nomogram in the training and validation sets were 0.898 and 0.823, respectively. After performing 100 iterations of 10-fold cross-validation, the goodness of fit (R²), area under the curve (AUC), Brier score, and maximum and minimum deviations from the ideal model (Emax and Eavg) all indicated that the nomogram exhibited good performance. CONCLUSIONS: The nomogram developed using CTCs and FAR enhances the early diagnosis of OPM and supports the formulation of personalized treatment plans for patients.