Abstract 476P
Background
Microsatellite status is a prognostic and predictive biomarker in locally advanced gastric cancer (LAGC) and its testing relies on pathological exam. The aim of our study is to build a predictive model for microsatellite status, based on preoperative computed tomography (CT) scan features.
Methods
We conducted a retrospective analysis of 40 patients with LAGC, treated with surgery and adjuvant/perioperative chemotherapy at Sant’Andrea Hospital of Rome, from August 2017 to January 2024, divided into microsatellite stable (MSS) and instable (MSI) group. All patients had baseline CT scan acquired with unhenanced, late arterial, and portal venous phase. A qualitative and quantitative assessment were performed by an expert blinded radiologist. In the qualitative analysis were evaluated cTN, cEMVI status, Dmax, cancer thickness, and peritumoral fatty infiltration. In the quantitative analysis were calculated: conventional CT-HU values, and delta contrast enhancement in all CT phases. All radiological features were compared between two groups (T-test or Mann–Whitney) and their significance was tested with ROC curve analysis. All features were used to build predictive models (qualitative, quantitative, and combined model) with multivariate logistic regression.
Results
13 and 27 patients presented MSI and MSS status, respectively. In prediction of MSI status, the tumor site and cancer thickness resulted to be significant (p<0.01) with AUC=0.72 and 0.75, respectively. In the univariate analysis the same features resulted to be independently correlated with MSS/MSI status with OR ≠ 1. The combined model, including all CT scan features, achieved an AUC=0.98 (P=0.0003), with a percentage of cases correctly classified of 92.5%. The qualitative model had an AUC=0.87 (P=0.01), while the quantitative model was not significant.
Conclusions
Our non invasive radiological model predicts the MSI/MSS status with a percentage of correctly classified cases of 92.5%.It can be useful to clinicians in to classify LAGC in MSS or MSI, then to select only patients suitable for chemotherapy. In particular, the radiological model could have the most relevance when pathological tissue is lacking or in urgency for bleeding or occlusion.
Legal entity responsible for the study
Federica Mazzuca.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.