## 1 Introduction  
Gastric cancer is one of the most common malignant tumors, and it ranks third worldwide in terms of mortality rates. Recently, with the increased progress in treatment approaches, patients with pathological stage I disease have achieved a cure rate of 90%; nevertheless, the prognosis of advanced gastric cancer is still poor in Europe, and the 5-year survival rate is reported to be about 25% [1,2]. Radical gastrectomy with D2 lymphadenectomy has historically been the milestone treatment for locally advanced gastric cancer (Stage IB-III) [3,4]. Since the publication of the MAGIC trial results showing that three preoperative and three postoperative cycles of epirubicin, cisplatin, and fluorouracil (ECF) improves progression-free and overall survival, the use of perioperative chemotherapy (p-ChT) has spread throughout Western countries [5]. Currently in Europe, the gold standard treatment for patients with locally advanced gastric cancer is radical gastrectomy with D2 lymphadenectomy and p-ChT with fluorouracil plus leucovorin, oxaliplatin, and docetaxel (FLOT) [6].  
The present trial compared the perioperative docetaxel-based triplet FLOT with an anthracycline-based triplet of either ECF or ECX (epirubicin, cisplatin, and capecitabine) for patients with resectable gastric or esophagogastric junction adenocarcinoma. The results of the trial showed that the patients treated with FLOT achieved a significantly higher rate of pathological complete regression (16% vs. 6%; \(p=0.02\)) associated with an improved overall survival with an estimated advantage of 15 months (50 vs. 35 months; \(p=0.012\)) when compared to the ECF/ECX group. However, not all patients are responders who can benefit from this approach. In non-responder patients, costly and ineffective preoperative chemotherapy could be avoided if they are assessed beforehand [7, 8, 9]. Currently, the only objective method of determining whether a patient has responded to preoperative chemotherapy is the evaluation of the tumor regression grade (TRG) of a surgical specimen. In order to exclude non-responder patients from preoperative chemotherapy, a diagnostic method to discriminate responder and non-responder patients should be identified at the time of the diagnosis.  
Radiomics is a tool able to extract ultrastructural quantitative data from previously acquired medical images (e.g., computed tomography, magnetic resonance imaging, ultrasound), providing features that characterize the spatial relationships of signal intensities in a specific tissue (e.g., a tumoral lesion) [10]. Radiomics has already demonstrated its usefulness in predicting treatment response across a range of cancer types and imaging modalities [10, 11, 12, 13, 14, 15]. Regarding gastric cancer, CT radiomics has already been shown to be a promising preoperative non-invasive prognostic biomarker [16]. Pre-treatment radiomics extracted from a baseline CT examination could also be used to provide important information about the response rate to preoperative chemotherapy for gastric cancer. This would improve patients' chances of selection for multimodal treatment [17,18]. Therefore, radiomics may represent an innovative non-invasive biomarker for the response to perioperative chemotherapy in locally advanced gastric cancer. Thus, the aim of this study is to assess the performance of CT radiomics in predicting the response to perioperative chemotherapy with a FLOT regimen in gastric cancer patients.