Diagnostic Value Of ¹⁸F-FDG PET/CT And CECT In Gastric Cancer With Different Signet Ring Cell Components

Part I:Diagnostic value of ¹⁸F-FDG PET/CT in gastric cancer with different signet ring cell componentsObjective:To investigate the diagnostic value of ¹⁸F-FDG PET/CT in gastric cancer with different signet ring cell components.Methods:The clinical data of 108 patients with gastric adenocarcinoma（GAC）who underwent ¹⁸F-FDG PET/CT examination were retrospectively analyzed.All patients were diagnosed by gastroscopy biopsy or surgical pathology,and were divided into gastric signet ring cell carcinoma（SRC）group,mixed signet ring cell carcinoma（Mixed-SRC）group and non-signet ring cell adenocarcinoma（Non-SRC）group according to the composition of signet ring cell.The imaging features of ¹⁸F-FDG PET/CT in primary lesions,lymph node metastasis and distant metastasis of gastric cancer with different signet ring cell components were analyzed by two experienced PET/CT diagnosticians,and the diagnostic value was evaluated by histopathological results and clinical follow-up as the reference standard.Results:In this study,108 patients with gastric adenocarcinoma were 13 patients with SRC,31 patients with Mixed-SRC and 64 patients with Non-SRC.There were 13 patients in the early stage and 95 patients in the advanced stage.The mean SUVmax of primary lesions in early patients and advanced patients were 3.9±2.3 and 10.7±7.7,respectively（P<0.05）.Among the 13 early patients,there were 5 cases of Mixed-SRC and 8 cases of Non-SRC,and the mean SUVmax of primary lesions was 4.8±3.4 and 3.3±1.2,respectively（P>0.05）.The detection rates of primary lesions in early Mixed-SRC and Non-SRC patients by¹⁸F-FDG PET/CT were 60.0%（3/5）and 62.5%（5/8）,respectively（P>0.05）.Among the 95advanced patients,there were 13 patients with SRC,26 patients with Mixed-SRC and 56patients with Non-SRC.The mean SUVmax of primary lesions was 6.4±3.3,8.5±5.0 and12.7±8.7,respectively（P<0.05）.The detection rates of primary lesions by ¹⁸F-FDG PET/CT in advanced SRC,Mixed-SRC and Non-SRC patients were 84.6%（11/13）,96.2%（25/26）and 98.2%（55/56）,respectively.The detection rate of ¹⁸F-FDG PET/CT in Mixed-SRC group and Non-SRC group was higher than that in SRC group,although the difference was not statistically significant（P=0.067）.In 81 patients with perigastric lymph node metastasis,the sensitivity of ¹⁸F-FDG PET/CT in detecting perigastric lymph node metastasis in patients with SRC,Mixed-SRC and Non-SRC was 63.6%（7/11）,69.6%（11/23）and 83.0%（39/47）,respectively（P>0.05）.In 36 patients with distant lymph node metastasis,the sensitivity of ¹⁸F-FDG PET/CT in detecting distant lymph node metastasis in patients with SRC,Mixed-SRC and Non-SRC were 60%（3/5）,100%（9/9）and 100%（22/22）,respectively,and the difference was statistically significant（P<0.05）.The sensitivity of ¹⁸F-FDG PET/CT in detecting distant lymph node metastasis in Mixed-SRC group and Non-SRC group was higher than that in SRC group.Distant metastasis was found in 43 cases,and the sensitivity of ¹⁸F-FDG PET/CT for the diagnosis of distant metastasis in patients with SRC,Mixed-SRC and Non-SRC was71.4%（5/7）,91.7%（11/12）and 100%（24/24）,respectively,with statistically significant differences（P<0.05）.¹⁸F-FDG PET/CT was more sensitive in detecting distant metastasis in the Mixed-SRC group and Non-SRC group than in the SRC group.Based on the number of distant metastatic lesions with a total of 75 metastases,the diagnostic sensitivity of ¹⁸F-FDG PET/CT in the three groups of patients with SRC,Mixed-SRC and Non-SRC was 60.0%（6/10）,90.0%（18/20）and 100%（45/45）,respectively,and the diagnostic sensitivity of¹⁸F-FDG PET/CT in the Mixed-SRC group and Non-SRC group was higher than that of the SRC group.Conclusions:¹⁸F-FDG PET/CT has unique advantages in the diagnosis of primary lesions in patients with advanced gastric cancer,but has poor performance in patients with early gastric cancer.¹⁸F-FDG PET/CT has a good application value in the diagnosis and staging of gastric cancer with different signet ring cell components,but its value in the diagnosis and staging of SRC is limited compared with Mixed-SRC and Non-SRC.Part II: Diagnostic significance of ¹⁸F-FDG PET/CT and CECT in gastric cancer with different signet ring cell componentsObjective: To investigate the diagnostic difference between ¹⁸F-FDG PET/CT and CECT in gastric cancer with different signet ring cell components.Methods: The clinical data of 96 patients with gastric adenocarcinoma（GAC）who underwent ¹⁸F-FDG PET/CT and CECT were retrospectively analyzed.All patients were diagnosed by gastroscopic biopsy or surgical pathology.The patients were divided into gastric signet ring cell carcinoma（SRC）group,mixed signet ring cell carcinoma（Mixed-SRC）group and non-signet ring cell adenocarcinoma（Non-SRC）group according to the composition of signet ring cell.The imaging features of ¹⁸F-FDG PET/CT and CECT in the primary lesion,lymph node metastasis and distant metastasis of gastric cancer with different components of signet ring cell carcinoma were analyzed by two experienced PET/CT diagnosticians and two radiologists,respectively.Histopathological findings and clinical follow-up were used as reference standards to evaluate the diagnostic differences between the two methods.Results: In this study,there were 96 patients with gastric adenocarcinoma,including 11 patients with SRC,28 patients with Mixed-SRC,and 57 patients with Non-SRC.The diagnostic compliance rates of ¹⁸F-FDG PET/CT and CECT for primary lesions in patients with SRC,Mixed-SRC and Non-SRC were 90.9%（10/11）and 90.9%（10/11）（P > 0.05）,89.3%（25/28）and 89.3%（25/28）（P > 0.05）,93.0%（53/57）and 71.9%（41/57）（P < 0.05）,respectively.In 11 early patients and 95 advanced patients,the diagnostic compliance rates of¹⁸F-FDG PET/CT and CECT were 54.5%（6/11）and 36.4%（4/11）（P > 0.05）in early stage patients and 96.5%（82/85）and 84.7%（72/85）（P < 0.05）in advanced patients.In 72 patients with perigastric lymph node metastasis,the diagnostic sensitivities of¹⁸F-FDG PET/CT and CECT for perigastric lymph node metastasis were 60.0%（6/10）and80.0%（8/10）（P > 0.05）,66.7%（14/21）and 71.4%（15/21）（P > 0.05）,80.5%（33/41）and 80.5%（33/41）（P > 0.05）.In 31 patients with distant lymph node metastasis,the diagnostic sensitivities of ¹⁸F-FDG PET/CT and CECT for distant lymph node metastasis in patients with SRC,Mixed-SRC and Non-SRC were 60.0%（3/5）and 80.0%（4/5）（P > 0.05）,100%（7/7）and 85.7%（6/7）（P > 0.05）,100%（19/19）and 89.5%（17/19）（P > 0.05）,respectively.Distant metastases were found in 39 patients,and the sensitivities of distant metastases in¹⁸F-FDG PET/CT and CECT for the diagnosis of SRC,Mixed-SRC and Non-SRC were71.4%（5/7）and 100%（7/7）（P > 0.05）,90.0%（9/10）and 90.0%（9/10）（P > 0.05）,100%（22/22）and 95.5%（21/22）（P > 0.05）,respectively.Based on the number of distant metastases,a total of 63 metastases,the detection rates of distant metastatic lesions in patients with SRC,Mixed-SRC and Non-SRC were 60.0%（6/10）and 90.0%（9/10）（P > 0.05）,87.5%（14/16）and 75.0%（12/16）（P > 0.05）,100%（37/37）and 62.2%（23/37）（P < 0.05）.Conclusion: On detection of the primary lesion,the diagnostic performance of ¹⁸F-FDG PET/CT was better than that of CECT in advanced patients,whereas in early patients,there was no significant difference between them;In patients with Non-SRC,¹⁸F-FDG PET/CT had a higher diagnostic yield compared to CECT;They were comparable in patients with SRC and Mixed-SRC.On lymph node metastasis diagnosis,there was no significant difference between them.On distant metastatic lesion detection,more occult metastases could be detected by ¹⁸F-FDG PET/CT than CECT in patients with Non-SRC;In patients with SRC and Mixed-SRC,there were no significant differences.