The Significance of CEA and CA 19-9 Levels in Serum and Peritoneal Fluid in Colorectal Cancer Patients in the Context of Peritoneal Metastases and Cytology Results.

Background/objectives: Colorectal cancer (CRC) frequently metastasizes to the peritoneum, significantly worsening patient prognosis. While serum tumor markers such as carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9) are routinely measured, their diagnostic or prognostic role in peritoneal fluid remains unclear. This study aimed to assess the relationship between CEA and CA 19-9 levels in both serum and peritoneal fluid, and the clinical stage of CRC, particularly focusing on the presence of peritoneal metastases and positive cytology.

Methods: We retrospectively analyzed data from 89 patients with histologically confirmed CRC who underwent surgery between 2020 and 2023. All patients had preoperative assessment of CEA and CA 19-9 levels in serum and peritoneal fluid, along with cytological examination of peritoneal fluid samples. Patients were categorized based on the presence or absence of macroscopic peritoneal metastases and cytology results.

Results: Elevated levels of CEA and CA 19-9 in peritoneal fluid were significantly associated with the presence of peritoneal metastases. A positive cytological finding also correlated with higher marker concentrations.

Conclusions: CEA and CA 19-9 levels in peritoneal fluid strongly correlate with peritoneal dissemination in CRC. These markers may serve as additional predictive factors, aiding in early detection of peritoneal spread and improved risk stratification. Their assessment may be useful in guiding intraoperative and postoperative decision-making.