Comparison of CT and 18F-FDG pet for detecting peritoneal metastasis on the preoperative evaluation for gastric carcinoma

Abstract

Objective: The aim of our study was to compare the accuracy of CT and (18)FFDG PET for detecting peritoneal metastasis in patients with gastric carcinoma.

Materials and methods: One-hundred-twelve patients who underwent a histologic confirmative exam or treatment (laparotomy, n = 107; diagnostic laparoscopy, n = 4; peritoneal washing cytology, n = 1) were retrospectively enrolled. All the patients underwent CT and (18)F-FDG PET scanning for their preoperative evaluation. The sensitivities, specificities and accuracies of CT and (18)FFDG PET imaging for the detection of peritoneal metastasis were calculated and then compared using Fisher's exact probability test (p < 0.05), on the basis of the original preoperative reports. In addition, two board-certified radiologists and two board-certified nuclear medicine physicians independently reviewed the CT and PET scans, respectively. A receiver-operating characteristic curve analysis was performed to compare the diagnostic performance of CT and (18)F-FDG PET imaging for detecting peritoneal metastasis.

Results: Based on the original preoperative reports, CT and (18)F-FDG PET showed sensitivities of 76.5% and 35.3% (p = 0.037), specificities of 91.6% and 98.9% (p = 0.035), respectively, and equal accuracies of 89.3% (p = 1.0). The receptor operating characteristics curve analysis showed a significantly higher diagnostic performance for CT (Az = 0.878) than for PET (Az = 0.686) (p = 0.004). The interobserver agreement for detecting peritoneal metastasis was good (kappa value = 0.684) for CT and moderate (kappa value = 0.460) for PET.

Conclusion: For the detection of peritoneal metastasis, CT was more sensitive and showed a higher diagnostic performance than PET, although CT had a relatively lower specificity than did PET.

Fig. 1

A 62-year-old man with poorly differentiated adenocarcinoma of the stomach. A. The transverse contrast enhanced CT scan shows multifocal peritoneal implants in the omentum (arrows). B. The PET image shows the diffuse FDG uptake that obscures the visceral outlines in the peritoneal cavity (arrows). Peritoneal metastasis was confirmed by diagnostic laparoscopy.

Fig. 2

A 60-year-old man with poorly differentiated adenocarcinoma of the stomach. A. The transverse contrast enhanced CT scan shows a peritoneal implant (arrow) in the right paracolic gutter. B. The PET image shows a discrete focus (arrow) of increased FDG metabolism in the same location. Peritoneal metastasis was confirmed by laparotomy.

Fig. 3

A 31-year-old man with poorly differentiated adenocarcinoma of the stomach. A. The transverse contrast enhanced CT scan shows multifocal peritoneal implants in the omentum (arrows). B. The transverse CT scan also shows ascitic fluid in the right paracolic gutter (arrows). The CT reviewers interpreted these findings as being highly suggestive of peritoneal metastasis. C. The PET image does not show significantly increased FDG uptake in the peritoneal cavity, except for the normal physiologic colon uptake in the ascending colon. Peritoneal metastasis was confirmed by laparotomy.

Fig. 4

A 72-year-old man with moderately differentiated adenocarcinoma of the stomach. A. Multiple tiny soft tissue infiltrations are suspected in the right paracolic gutter on the CT image (arrows). The CT reviewers interpreted this finding as being peritoneal metastasis. B. The PET image does not show significantly increased FDG uptake in the peritoneal cavity. The absence of peritoneal metastasis was identified by laparotomy.

Fig. 5

Plot showing the receiver operating characteristic curves for detecting peritoneal metastasis with using CT (solid line) and PET (dotted line).