Prediction of Peritoneal Dissemination of Digestive Tumors Through the Study of Circulating Tumor DNA

The peritoneum is a relatively frequent metastatic site in digestive tumors (colon, stomach, pancreas) and is characterized by a poorer prognosis compared with other metastatic sites such as the lung or liver. Its dissemination pathway is complex and most often involves crossing the hemato-peritoneal barrier. This type of metastasis is difficult to visualize on imaging at an early stage, and surgical exploration may be required. In gastric cancer in particular, exploratory laparoscopy is part of the initial staging work-up for locally advanced tumors to assess the presence or absence of peritoneal metastases. It is therefore important to develop new, less invasive detection or prediction methods. Circulating tumor DNA (ctDNA) is a promising non-invasive blood biomarker that can assist clinicians as a prognostic/predictive biomarker and/or a tool for monitoring response to anti-tumor therapies. This marker is most often assessed in plasma, but recent data suggest that tumor DNA may also be detected in other biological fluids such as peritoneal fluid. A preliminary study conducted by our team showed the ability to detect tumor DNA in peritoneal fluid from patients with peritoneal carcinomatosis of various origins, with a sensitivity of 75%. In gastric cancer, a recent meta-analysis demonstrated an increased risk of peritoneal metastases when peritoneal tumor DNA was positive (RR 13.81 \[95% CI, 8.11-23.53\]), as well as a reduction in 3-year recurrence-free survival (RR 5.37 \[95% CI, 1.39-20.74\]) and overall survival (HR 4.13 \[95% CI, 1.51-11.32\]). The objective of this cohort is to evaluate the prognostic impact of circulating tumor DNA (ctDNA) in plasma and/or peritoneal fluid on the risk of developing peritoneal metastases. The primary endpoint is: Peritoneal recurrence rate according to tumor DNA positivity status (positive vs negative).

Sex

All

Minimum age

18 Years

Inclusion Criteria:

* Age \> 18 years
* Signed non-opposition form
* For gastric cancer: histologically confirmed gastric adenocarcinoma \>T2 and/or N+; for colon cancer: histologically confirmed colonic adenocarcinoma \>T2; for pancreatic cancer: histologically confirmed pancreatic adenocarcinoma \>T2
* No metastases on the initial staging work-up
* No contraindication to curative-intent surgical treatment

Exclusion Criteria:

* Primary tumor metastatic at diagnosis
* Presence of ascites or distant metastases
* Synchronous cancer or prior history of cancer within the past 5 years
* Contraindication to curative surgical treatment
* Any patient unable to comply with the study's medical follow-up for geographic, social, or psychological reasons
* Patients under legal guardianship/protection, or unable to read, understand, and sign the information notice and consent form
* Patients not affiliated with the social security system