FDG PET/CT vs Staging Laparoscopy for Occult Metastases in Locally Advanced Gastric Adenocarcinoma: A Prospective Comparative Diagnostic Study

Abstract

Introduction: Gastric cancer is an aggressive malignancy with a high risk of peritoneal spread. Accurate staging is critical to optimize treatment strategies and avoid unnecessary laparotomies. While PET-CT provides information on nodal and distant disease, staging laparoscopy allows direct visualization of peritoneal and liver involvement.

Materials and Methods: This was a prospective; single-centre diagnostic study conducted at IMS & SUM Hospital, Bhubaneswar, including 42 consecutive patients with newly diagnosed, locally advanced, non-metastatic gastric adenocarcinoma (cT3–4a, N0–3, M0). All patients underwent baseline contrast-enhanced CT, followed by both PET-CT and staging laparoscopy with peritoneal wash cytology. The primary endpoint was paired sensitivity of PET-CT versus staging laparoscopy in detecting peritoneal disease. Diagnostic yield and detection rates were compared.

Results: Among 42 patients (73.8% male; median age 57 years), staging laparoscopy identified peritoneal disease in 9/42 (21.4%, 95% CI 10.9–36.9), whereas PET-CT detected none (0/42; McNemar p < 0.001). PET-CT demonstrated perigastric nodal uptake in 37/42 (88.1%, 95% CI 74.4–95.6), but nodal status could not be confirmed pathologically. Staging laparoscopy detected liver metastases in 2/42 (4.7%) and omental deposits in 6/42 (14.2%), all of which were missed on PET-CT. Histopathology of M1 cases revealed poorly differentiated variants, predominantly signet ring and mucinous adenocarcinoma. Overall, staging laparoscopy altered management in 16/42 (43%) patients by redirecting them to neoadjuvant chemotherapy or palliative care.

Conclusions: PET-CT alone is inadequate for detecting peritoneal disease in locally advanced gastric cancer. Staging laparoscopy remains indispensable, especially in poorly differentiated tumors, and significantly impacts treatment planning. Integration of PET-CT with staging laparoscopy provides the most reliable approach for accurate staging and optimal patient management.