Sequential 18F-FDG PET/CT and contrast-enhanced CT in the pretreatment staging of gastric cancer

Objective To evaluate the value of sequential 18F-FDG PET/CT and CECT (PET/CT+ CECT) in the pretreatment staging of gastric cancer,and to analyze the factors affecting the uptake of 18F-FDG in gastric cancer.Methods A total of 28 untreated gastric cancer patients (23 males,5 females,age (62.0± 11.3) years) confirmed by endoscopy biopsy were selected for this prospectively study.18F-FDG PET/CT was performed first,followed by 3-phase abdominopelvic CECT in the same position.They were compared in terms of their efficacy in primary gastric tumor detection,and accuracy in finding peri-gastric lymph node and abdominopelvic organ metastasis.Pearson correlation analysis,Kappa test,Mann-Whitney u test,Kruskal-Wallis H test,paired x2 test were used.Results Of 12 stage Ⅳ inoperable patients,18F-FDG PET/CT revealed 3 more small liver metastases in 2 patients which were negative on CECT.In 16 patients who underwent gastrectomy and lymph node dissection,all primary tumors were positive on CECT while 15/16 were positive on PET (SUVmax 3.15-19.99).The remaining case was a poorly differentiated signet-ring gastric adenocarcinoma with mild uptake (SUVmax 1.62).In all 16 patients,there was moderate correlation between primary tumor volume and SUVmean (r =0.573,95％ CI:0.108-0.832,P＜ 0.05).The consistency of serosal infiltration evaluated by CECT was low as compared with post-operative pathology (κ=0.143,95％ CI:-0.338-0.624).There was no significant statistical correlation between SUVmax of primary tumors with presence/absence of vascular or perineural infiltration,different T staging and histological grades (u=27.00,H=4.79 and 1.99,all P＞0.05).A total of 399 lymph nodes were dissected from the 16 patients;81 were confirmed metastatic.The evaluation of lymph node metastasis by PET/CT and CECT was not consistent but complementary.The sensitivity,specificity,accuracy,PPV and NPV for the detection of lymph node metastasis were 10/10,1/6,11/16,10/15 and 1/1 for CECT;6/10,6/6,12/16,6/6 and 6/10 for PET/CT;and 10/10,4/6,14/16,10/12 and 4/4 for PET/CT+CECT.Conclusions 18F-FDG PET/CT is superior to CECT for detection of small liver metastasis.18F-FDG PET/CT+CECT can improve the accuracy of pretreatment staging of gastric cancer.