Assessment of the reliability of MSI status and dMMR proteins deficiency screening on endoscopic biopsy material in esophagus and gastric adenocarcinoma

Computed tomography features of gastric cancer with deficient mismatch repair: Radiologic-pathologic correlation

OBJECTIVES

Our study aimed to identify CT features of locally advanced gastric cancer (LAGC) associated with deficient mismatch repair (dMMR), explore the underlying pathological basis, and develop a morphology-based model for dMMR prediction.

METHODS

This multicenter, retrospective analysis included 397 patients with LAGC treated at three institutions between January 2016 and January 2022. Mismatch repair (MMR) status was determined by immunohistochemical analysis of postoperative specimens. The patients were divided into training and external validation groups. CT features of primary tumours and lymph nodes associated with MMR status were identified, and the underlying pathological basis for these features were explored. Multivariable logistic analysis was used to identify independent CT features and to develop a morphology-based model.

RESULTS

Tumours with dMMR were characterized by increased thickness (p = 0.04), location in the lower stomach (p < 0.001), heterogeneous enhancement patterns (p = 0.02), a well-defined margin (p < 0.001), the presence of mushroom sign (p < 0.001), and the presence of abnormal lymph nodes (p = 0.07). Pathologically, tumours with dMMR exhibited extensive lymphocytic infiltration and solid growth with a pushing border, consistent with the distinctive CT features observed. Multivariable logistic analysis identified lower tumour location, well-defined tumour margin, and mushroom sign as independent predictors of dMMR. The morphology-based model achieved AUC values of 0.73-0.74 for dMMR prediction in the training and external validation groups.

CONCLUSIONS

LAGC with dMMR showed distinct CT features. A morphology-based model constructed from these CT features has the potential to predict dMMR status for LAGC.

How do I treat dMMR/MSI gastro-oesophageal adenocarcinoma in 2025? A position paper from the EORTC-GITCG gastro-esophageal task force

In less than a decade, immune checkpoint inhibitors (ICIs) have transformed the management of mismatch repair-deficient (dMMR) and microsatellite instability-high (MSI) cancers. However, beyond colorectal cancer (CRC), much of the evidence is mostly derived from non-randomized phase II studies or post-hoc analyses of broader clinical trials. dMMR/MSI tumours represent a specific subgroup of gastro-esophageal adenocarcinomas (GEA), accounting for approximately 9 % of cases, with a higher prevalence in early-stage compared to advanced-stage disease and older female patients. These tumours are predominantly sporadic, often linked to MLH1 promoter methylation, and rarely exhibit HER2 overexpression/ERBB2 amplification or other oncogenic drivers. The treatment landscape for early stage dMMR/MSI GEA is likely to change substantially soon, as ICIs have shown high pathological complete response (pCR) rates in small phase II trials, raising questions on optimisation of neoadjuvant therapy, and paving the way for organ preservation. The standard of treatment for untreated patients with advanced dMMR/MSI GEA is chemotherapy + ICI irrespectively of PDL-1 status. However, the role of chemotherapy-free regimen consisting of CTLA-4 plus PD-1 inhibitors remains undetermined. This review addresses these and other emerging questions, offering expert opinions and insights into the future therapeutic landscape for dMMR/MSI GEA.

Management of esogastric cancer in older patients

Although esogastric cancers often affect patients over 75, there are no specific age-related guidelines for the care of these patients. Esogastric cancers have a poor prognosis and require multimodal treatment to obtain a cure. The morbidity and mortality of these multimodal treatments can be limited if care is optimized by selecting patients for neoadjuvant treatment and surgery. This can include a geriatric assessment, prehabilitation, renutrition, and more extensive use of minimally invasive surgery. Denutrition is frequent in these patients and is particularly harmful in older patients. While older patients may be provided with neoadjuvant chemotherapy or radiotherapy, it must be adapted to the patient's status. A reduction in the initial dose of palliative chemotherapy should be considered in patients with metastases. These patients tolerate immunotherapy better than systemic chemotherapy, and a strategy to replace chemotherapy with immunotherapy whenever possible should be evaluated. Finally, better supportive care is needed in patients with a poor performance status. Prospective studies are needed to improve the care and prognosis of elderly patients.