| Objective Gastric cancer is the most common tumor in the digestive system with a poor prognosis and is the second most frequent cause of cancer-related death worldwide. Currently CT is the main diagnostic technique in the staging of gastric cancer preoperation but the accuracy of detecting regional lymph nodes and distant metastasis is not high. But 18F-FDG PET/CT imaging has shown a larger advantage in these two areas. So the aim of this study was to evaluate the clinical value of PET/CT in diagnosing and staging of gastric cancer.Materials and Methods Sixty-nine patients (47 males,22 females, aged 21-91 years) suspected of gastric cancer were included and underwent whole body 18F-FDG PET/CT imaging after taking in 400-550ml of water to distend the stomach cavity. Data of PET scan were reconstructed and fused with CT slices. PET, CT and fusion images were displayed in three orthogonal projections. Images were interpreted on the Xeleris workstation and all of the PET images were reviewed visually and semi-quantitatively. PET images were reviewed in conjunction with relevant the CT and the fused images used to identify malignant and benign lesions, and diagnose standard preoperative staging. The maximum standard uptake value(SUVmax) of gastric primary lesions and regional lymph nodes in PET and the maximum thickness(Tmax) of the gastric wall in CT were analyzed. Pathological specimens were obtained from all the patients during surgery or gastroscopy. SPSS 13.0 statistical package was used to analyze in this study. P＜0.05 was considered statistically significant.Results In 69 patients, primary lesions of 40 patients were confirmed by gastroscopy and 29 patients by surgery. There were 58 cases of gastric cancer,4 primary gastric lymphoma,1 malignant gastrointestinal stromal tumors,1 gastric ulcer,3 gastritis and 2 normality. The sensitivity, specificity and accuracy of 18F-FDG PET/CT in identifying stomach neoplasms were 93.65%(59/63),83.33%(5/6) and 92.75%(64/69), respectively. The sensitivity of PET/CT in detecting gastric primary lesions was 93.10%(54/58), one case of mucinous gastric carcinoma and 3 cases of early-stage gastric cancer(T1) gave false negative results. And we found a significant positive correlation between SUVmax and Tmax(r=0.539, P=0.000). In the 27 patients confirmed by surgery, the sensitivity, specificity and accuracy of PET/CT in identifying regional lymph nodes were 65.22%(15/23),100.00%(4/4) and 70.37% (19/27), respectively. The overall accuracy of PET/CT in the staging of regional lymph nodes was 59.26%, especially for N3 lymph nodes(100%). And we also found a significant positive correlation between the SUVmax of regional lymph nodes and of primary lesions(r=0.618, P=0.000). PET/CT detected 11 patients with distant lymph nodes metastasis, hematogenous metastasis in 15 cases and 10 of peritoneal metastasis. In additional, PET/CT imaging detected two second primary cancers, which were stomach neoplasms associated with differentiated adenocarcinoma in the descending colon and endometrial carcinoma, respectively.Conclusion 18F-FDG PET/CT has a high sensitivity in diagnosing primary lesions of advanced gastric cancer, but not suitable for early-stage gastric cancer screening. PET/CT imaging can significantly increase the diagnostic accuracy of staging of gastric cancer. PET/CT is one of the rational ways to accurately assess the biological behavior of gastric cancer and provide a basis for optimal treatment strategies to clinical doctors. PET/CT imaging has an important value in the location and qualitative diagnostic of stromal tumors and staging of gastric lymphoma. At the same time, it is useful for detecting a second primary cancer with a high sensitivity. However, other clinical information including conventional imaging should also be investigated to reduce the number of false-positive and false-negative cases. |
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