Evaluation of the Reliability of the Determination of MisMatch Repair Deficiency Status by Endoscopic Biopsies in Oesophagus and Gastric Adenocarcinoma.

Overview

Gastro-esophageal adenocarcinoma is one of the most common cancer in the world and the fourth most common cancer in France with more than 6,000 cases per year. For non-metastatic patients, a preoperative chemotherapy is recommended. As colorectal adenocarcinomas, gastroesophageal cancers (OGC) could be caused by a failure of DNA repair related to the loss of expression of one of the DNA repair proteins (MLH1, MSH2, PMS2, MSH6) (deficient MMR (dMMR)). The prevalence of tumors with dMMR is evaluated at 14% (Choi et al, 2014; Kim et al, 2015). This proportion reaches 25% among patients over 70 years old. Evidence suggests that patients with dMMR tumors do not benefit from neoadjuvant chemotherapy (Smyth et al, 2017), which may even have a negative impact, especially in elderly patients, and which should be discussed in this particular situation. The decision of neo-adjuvant chemotherapy must be taken very quickly after the endoscopic diagnosis. The investigators will evaluate the diagnostic performance of the determination of dMMR status by endoscopic biopsies of OGC. Moreover, there is no clear recommendation for the determination of dMMR status in OGC especially regarding the size of the forceps to use to ensure the quality of samples and the best molecular techniques for dMMR status determination. Methods In this prospective study, the investigators will include patients who will benefit from an upper endoscopy within 5 French hospital centers (Saint-Louis, Lariboisière, Beaujon, Bichat and Avicenne) linked to the NORDICAP network. If a suspect lesion of OGC is discovered during the gastroscopy, the endoscopist will perform at least 8 endoscopic biopsies, according to the recommendations, and by the mean of 2 kinds of forceps: standard biopsy forceps and a large capacity biopsy forceps. The clinical and follow-up data will be prospectively collected and will include demographics data, cancer stage, lymph node invasion, treatment history, recurrence and survival data. The investigators will assess MSI status by genotyping and MMR proteins expression by immunochemistry (IHC), performed, for each patient, on both biopsies and surgical tumor samples. Expected results This study will allow us to compare diagnostic performance of endoscopic biopsies to surgical samples for the assessment of dMMR status. Likewise, the investigators will compare the diagnostic performance of the two kinds of endoscopic forceps and of IHC and genotyping for the determination of dMMR phenotype. It will enable us to establish recommendations for the benefit of gastro-enterologists and pathologists.