Liquid Biopsies for the Personalized Management of Patients with Hereditary Diffuse Gastric Cancer

Carriers of germline pathogenic variants in the CDH1 and CTNNA1 genes have the Hereditary Diffuse Gastric Cancer Syndrome. Asymptomatic carriers have at high lifetime risk of diffuse gastric cancer (30-70%). Screening upper gastrointestinal endoscopy, even with multiple random biopsies, misses signet ring cell cancer foci. Invasive cancers can thus go undetected. There is therefore a recommendation of total risk-reducing gastrectomy, at least in carriers with a family history of gastric cancer. Novel screening strategies are needed. In this pilot project, the investigators will perform liquid biopsies of both blood and gastric fluid in asymptomatic carriers who refuse gastrectomy and in controls. The investigators aim to show that somatic mutations in a panel of genes involved in gastric cancer and methylation profiles are detected in a subset of carriers, and not in controls. These could be indicative of invasive cancer undetected by endoscopy, and would thus be a strong argument for risk-reducing gastrectomy. On the contrary, in the absence of somatic mutations in liquid biopsies, endoscopic surveillance could continue.

Inclusion criteria

Case:

• Patient ≥ 18 years old
• CDH1 or CTNNA1 germline pathogenic variant.
• No history of diffuse gastric cancer.
• French social security.
• Ability to understand and willingness to sign a written informed consent document.

Volunteers:

• Patients ≥ 18 years old
• Patients with no oncological history
• Patients with macroscopically normal oeso-gastroduodenal fibroscopy
• French social security.
• Ability to understand and willingness to sign a written informed consent

Exclusion criteria

for both arms

• Patients with cancer being treated
• Patients with metastatic cancer
• Medical contraindication to general anesthesia or FOGD (bleeding disorder, pregnant women )
• Patients under guardianship or curator