What is the best staging method for peritoneum in gastric cancer?

Diagnostic Laparoscopy with Peritoneal Washings is the Best Staging Method for Peritoneum in Gastric Cancer

Diagnostic laparoscopy with peritoneal washings for cytology is the best staging method for peritoneal assessment in gastric cancer due to its high sensitivity (84.6%) and specificity (100%) in detecting peritoneal metastases that are often missed by conventional imaging techniques. 1

Limitations of Conventional Imaging Techniques

• CT scanning is routinely used for preoperative staging but has limited sensitivity (28-51%) despite high specificity (97-99%) for detecting peritoneal metastases 2
• Endoscopic ultrasound (EUS) is valuable for T and N staging but has limited utility for peritoneal assessment due to restricted depth and visualization of the transducer 2
• FDG-PET/CT has low detection rates for peritoneal disease due to low tracer accumulation in diffuse and mucinous tumor types common in gastric cancer 2
• FDG-PET detects only 3% of occult peritoneal metastases compared to 19% detected by diagnostic laparoscopy 2

Advantages of Diagnostic Laparoscopy with Peritoneal Washings

• Allows direct visualization of peritoneal surfaces and targeted biopsies of suspicious lesions 3
• Peritoneal washing cytology can identify occult carcinomatosis not visible on imaging or even during laparoscopic examination 2
• Positive peritoneal cytology is an independent predictor for identifying patients at higher risk for recurrence following curative resection 2
• Can detect radiographically occult metastatic disease in 31% of patients with potentially resectable gastric cancer 2

Clinical Recommendations for Peritoneal Staging

• Diagnostic laparoscopy with peritoneal washings is recommended for all stage IB-III gastric cancers that are considered potentially resectable 2
• The benefit is greater for patients with T3/T4 disease and poorly cohesive tumors 2
• NCCN guidelines recommend performing diagnostic laparoscopy to assess the peritoneal cavity (with biopsies as needed) and cytology of peritoneal washings in medically fit patients with potentially resectable stage cT1b or higher 2
• Peritoneal metastases should be documented according to the Peritoneal Carcinomatosis Index (PCI) 2

Clinical Implications of Peritoneal Staging Results

• Positive peritoneal cytology (CY+) even in the absence of visible peritoneal implants should be considered as M1 disease 2
• Surgery as initial treatment is not recommended for patients with positive peritoneal cytology 2
• A lower PCI score has been associated with better prognosis, and patients with limited peritoneal metastases might be appropriate candidates for cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC) 2
• Cases involving CY+ should be discussed in a multidisciplinary tumor board, weighing up the risks and potential benefit of surgery 2

Emerging Techniques for Peritoneal Assessment

• Whole-body diffusion-weighted magnetic resonance imaging has emerged as an alternative imaging modality for the diagnosis of peritoneal metastases 2
• Radiomic signatures based on CT phenotypes of primary tumors and adjacent peritoneum are being developed to improve the predictive capability of CT imaging for occult peritoneal metastases 2
• 5-aminolevulinic acid-mediated photodynamic diagnosis during staging laparoscopy is being evaluated for improved detection of peritoneal metastases 4

Practical Considerations and Limitations

• Limitations of laparoscopic staging include 2-dimensional evaluation and limited use in the identification of hepatic metastases and perigastric lymph nodes 2
• The procedure requires appropriate equipment and trained personnel to perform and interpret the findings 5
• Complications are rare but can include those related to anesthesia, access-related injuries, and potential tumor seeding at port sites 2